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Pressure Casting

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  • Countryside Models
    I usually pressurize my mixed urethane resin at about 45 PSI. If I were to increase the pressure to 75 PSI, would this make a big difference in (1) resin more
    Message 1 of 20 , Oct 1, 2000
      I usually pressurize my mixed urethane resin at about 45 PSI. If I were to
      increase the pressure to 75 PSI, would this make a big difference in (1)
      resin more fully filling the tiny nooks and cranies of my RTV mold and, (2)
      would it help to eliminate more air bubbles?

      The reason I wonder this is because I know that in vacuum systems, there is
      a big difference in performance when going from 27.5" Hg to 29 - 30 " Hg. I
      was wondering if this same kind of difference applied to pressure casting
      when going from 45 PSI up to some higher pressure.

      Regards,
      Ed Novit
      Countryside Models
    • lawrence jackman
      As it has been stated before, Pressure does not eliminate air bubbles. It just compress them to smaller ones. Higher the pressure the smaller the bubbles. A
      Message 2 of 20 , Oct 1, 2000
        As it has been stated before, Pressure does not
        eliminate air bubbles. It just compress them to
        smaller ones. Higher the pressure the smaller the
        bubbles. A vacuum causes the bubbles to expand and
        burst causing the air to be to be ejected from
        your casting and mold.
        Larry

        Countryside Models wrote:
        >
        > I usually pressurize my mixed urethane resin at about 45 PSI. If I were to
        > increase the pressure to 75 PSI, would this make a big difference in (1)
        > resin more fully filling the tiny nooks and cranies of my RTV mold and, (2)
        > would it help to eliminate more air bubbles?
        >
        > The reason I wonder this is because I know that in vacuum systems, there is
        > a big difference in performance when going from 27.5" Hg to 29 - 30 " Hg. I
        > was wondering if this same kind of difference applied to pressure casting
        > when going from 45 PSI up to some higher pressure.
        >
        > Regards,
        > Ed Novit
        > Countryside Models
        >
        > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in using your e-mail address and password. You will see a list of groups you are a member of. Choose the "Unsubscribe" option, from the drop down menu on the right. Then choose "Save Changes" at the bottom of the page. PLEASE DO NOT POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
      • Tom Banwell
        While Larry is technically correct, the air bubbles are made so small that they can t be seen, and even when inked--as we do in synthetic scrimshaw--they
        Message 3 of 20 , Oct 1, 2000
          While Larry is technically correct, the air bubbles are made so small that they can't be seen, and even when inked--as we do in synthetic scrimshaw--they retain no ink. So for all practical applications, the bubbles are gone. I use my pressure pot at 130 PSI. I would say you would definitely benefit by raising your pressure from 45 to 75 PSI..
          --
          Thanks, Tom
          http://www.lumicast.com


          lawrence jackman wrote:

          > As it has been stated before, Pressure does not
          > eliminate air bubbles. It just compress them to
          > smaller ones. Higher the pressure the smaller the
          > bubbles. A vacuum causes the bubbles to expand and
          > burst causing the air to be to be ejected from
          > your casting and mold.
          > Larry
          >
          > Countryside Models wrote:
          > >
          > > I usually pressurize my mixed urethane resin at about 45 PSI. If I were to
          > > increase the pressure to 75 PSI, would this make a big difference in (1)
          > > resin more fully filling the tiny nooks and cranies of my RTV mold and, (2)
          > > would it help to eliminate more air bubbles?
          > >
          > > The reason I wonder this is because I know that in vacuum systems, there is
          > > a big difference in performance when going from 27.5" Hg to 29 - 30 " Hg. I
          > > was wondering if this same kind of difference applied to pressure casting
          > > when going from 45 PSI up to some higher pressure.
          > >
          > > Regards,
          > > Ed Novit
          > > Countryside Models
          > >
          > > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in using your e-mail address and password. You will see a list of groups you are a member of. Choose the "Unsubscribe" option, from the drop down menu on the right. Then choose "Save Changes" at the bottom of the page. PLEASE DO NOT POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
          >
          > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in using your e-mail address and password. You will see a list of groups you are a member of. Choose the "Unsubscribe" option, from the drop down menu on the right. Then choose "Save Changes" at the bottom of the page. PLEASE DO NOT POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
        • Miracle Castings Inc.
          Hi! Just a note of caution here. Make sure your pressure vessel is rated for 75 psi before you go boosting that pressure! An exploded pressure vessel can be
          Message 4 of 20 , Oct 1, 2000
            Hi! Just a note of caution here. Make sure your pressure vessel is rated
            for 75 psi before you go boosting that pressure! An exploded pressure
            vessel can be fatal. Regards,

            Pat Lawless
            Moderator
            Miracle Castings Inc. - Manufacturers of fine resin model railroad kits.
            Web site: http://mc.cyklone.com/ Phone: (519) 757-2629
            ----- Original Message -----
            From: "Tom Banwell" <tom@...>
            To: <casting@egroups.com>
            Sent: Sunday, October 01, 2000 12:25 PM
            Subject: Re: [casting] Pressure Casting


            > While Larry is technically correct, the air bubbles are made so small that
            they can't be seen, and even when inked--as we do in synthetic
            scrimshaw--they retain no ink. So for all practical applications, the
            bubbles are gone. I use my pressure pot at 130 PSI. I would say you would
            definitely benefit by raising your pressure from 45 to 75 PSI..
            > --
            > Thanks, Tom
            > http://www.lumicast.com
            >
            >
            > lawrence jackman wrote:
            >
            > > As it has been stated before, Pressure does not
            > > eliminate air bubbles. It just compress them to
            > > smaller ones. Higher the pressure the smaller the
            > > bubbles. A vacuum causes the bubbles to expand and
            > > burst causing the air to be to be ejected from
            > > your casting and mold.
            > > Larry
            > >
            > > Countryside Models wrote:
            > > >
            > > > I usually pressurize my mixed urethane resin at about 45 PSI. If I
            were to
            > > > increase the pressure to 75 PSI, would this make a big difference in
            (1)
            > > > resin more fully filling the tiny nooks and cranies of my RTV mold
            and, (2)
            > > > would it help to eliminate more air bubbles?
            > > >
            > > > The reason I wonder this is because I know that in vacuum systems,
            there is
            > > > a big difference in performance when going from 27.5" Hg to 29 - 30 "
            Hg. I
            > > > was wondering if this same kind of difference applied to pressure
            casting
            > > > when going from 45 PSI up to some higher pressure.
            > > >
            > > > Regards,
            > > > Ed Novit
            > > > Countryside Models
            > > >
            > > > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in
            using your e-mail address and password. You will see a list of groups you
            are a member of. Choose the "Unsubscribe" option, from the drop down menu on
            the right. Then choose "Save Changes" at the bottom of the page. PLEASE DO
            NOT POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
            > >
            > > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in using
            your e-mail address and password. You will see a list of groups you are a
            member of. Choose the "Unsubscribe" option, from the drop down menu on the
            right. Then choose "Save Changes" at the bottom of the page. PLEASE DO NOT
            POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
            >
            >
            >
            >
            >
            > NOTE: TO UNSUBSCRIBE FROM THIS LIST: Go to egroups.com, and log in using
            your e-mail address and password. You will see a list of groups you are a
            member of. Choose the "Unsubscribe" option, from the drop down menu on the
            right. Then choose "Save Changes" at the bottom of the page. PLEASE DO NOT
            POST UNSUBSCRIBE MESSAGES ON THE LIST, AS THEY WILL BE IGNORED!
            >
          • sfrare
            Hi: I just joined this list and have never casted anything before. I would like to use Pressure Casting however the 2.5 gallon pots are a bit small. Does
            Message 5 of 20 , Jun 12, 2003
              Hi:

              I just joined this list and have never casted anything before. I
              would like to use 'Pressure Casting' however the 2.5 gallon pots are
              a bit small. Does anyone know of a site that shows how to build a
              pressure chamber? At 60 P.S.I. I want to be safe.

              Thank You
              Steve
            • mwhirailer
              Hi Steve, What exactly do you plan on casting? If your concern is to put a bunch of molds into one tank, as a beginner, save yourself some time and start with
              Message 6 of 20 , Jun 12, 2003
                Hi Steve,

                What exactly do you plan on casting? If your concern is to put a bunch of molds into one tank, as a beginner, save yourself some time and start with the little tank. If the goal is to create large molds, that's something entirely different. However, as a beginner I would still suggest that you start out small and work your way up to the bigger stuff. I say this with experience. I too wanted the big tanks in the beginning. I now have several small tanks that go through continuous service with small molds. I may have four molds cooking resin concurrently while demolding and prepping others for the same thing. It's sort of a round robbin affair.

                Hope this helps,
                Terry Wellman
                St. Charles, IL

                [Non-text portions of this message have been removed]
              • mwhirailer
                Oh yeah, one more thing. You would be fine with 40PSI in most applications. Why the mention of 60PSI? Terry [Non-text portions of this message have been
                Message 7 of 20 , Jun 12, 2003
                  Oh yeah, one more thing. You would be fine with 40PSI in most applications. Why the mention of 60PSI?

                  Terry

                  [Non-text portions of this message have been removed]
                • sfrare
                  Hi Terry: 60 P.S.I. is what I have read the pressure should be... The pressure tank I am currently looking at will do 80 P.S.I. so I should be okay, though it
                  Message 8 of 20 , Jun 12, 2003
                    Hi Terry:

                    60 P.S.I. is what I have read the pressure should be... The
                    pressure tank I am currently looking at will do 80 P.S.I. so I
                    should be okay, though it is a 2.5 gallon job and is a bit small but
                    will work for my current project.

                    We just cross posted I guess. I just posted what I am trying to do
                    in the following message:

                    http://groups.yahoo.com/group/casting/message/17716

                    Thank You
                    Steve

                    --- In casting@yahoogroups.com, "mwhirailer" <mwhirailer@a...> wrote:
                    > Oh yeah, one more thing. You would be fine with 40PSI in most
                    applications. Why the mention of 60PSI?
                    >
                    > Terry
                    >
                    > [Non-text portions of this message have been removed]
                  • mwhirailer
                    Hi Steve, Yeah I just saw the cross posts. No prob. You can get away with 40 PSI. 40 is enough to eliminate most air problems from your molds. When you
                    Message 9 of 20 , Jun 12, 2003
                      Hi Steve,

                      Yeah I just saw the cross posts. No prob. You can get away with 40 PSI. 40 is enough to eliminate most air problems from your molds. When you increase you run the risk of introducing new problems. Mike Jackson and Mike Brose both discussed the Urchin effect. I've seen blown molds because the PSI was set to 90 by another caster. Too much of a good thing can cause additional issues.

                      Terry


                      [Non-text portions of this message have been removed]
                    • dsbnumpsie
                      Hi folks, me again. Stop your groaning.. this won t hurt a bit, I promise. Anyway, I ve read lots recently about casting under pressure. Through reading,
                      Message 10 of 20 , Aug 15, 2003
                        Hi folks, me again. Stop your groaning.. this won't hurt a bit, I
                        promise.

                        Anyway, I've read lots recently about casting under pressure. Through
                        reading, reviewing and research I've learned that casting under
                        pressure forces air bubbles to the centre of the casting. Does this
                        mean that in effect you could create a hollow cavity in the casting,
                        or is that just wishful thinking?

                        Another thing I've wondered about is what the set time is with the
                        resin you guys are using for pressure casting. Smooth Cast 320 has a
                        3 minute working time, and roughly a 10 minute set time. Would a fast
                        curing resin like that be ok for pressure casting? Or is it more for
                        the slower set resins? I'm wondering if a tank would come up to
                        pressure fast enough for it to make a difference in a fast set resin.

                        See, completely painless :)

                        Jody
                      • Casting Fool
                        From: dsbnumpsie ... casting, or is that just wishful thinking? When you wish upon a bar, makes no difference where bubbles are.
                        Message 11 of 20 , Aug 15, 2003
                          From: "dsbnumpsie" <dsbnumpsie@...>
                          > Does this mean that in effect you could create a hollow cavity in the
                          casting, or is that just wishful thinking?

                          "When you wish upon a bar, makes no difference where bubbles are. They all
                          go where atoms are, your dreams come truuuuuuuue!"

                          > Another thing I've wondered about is what the set time...

                          I use Alumilite's Slow Set. 7 minutes from stir to cure. In my case that's
                          enough time to go from cup to mold to 48 psi. I'm currently adding a frame
                          so I can lay my tank on its side, too, for more room in the pot for larger
                          molds.

                          TTFN - Mike Jackson
                          Casting Fool & Son
                          Augusta, GA USA
                          http://www.cfnson.com
                        • Casting Fool
                          From: Casting Fool ... all go where atoms are, your dreams come truuuuuuuue! I m sorry, Jiminy Cricket told me that my meter, and rhyme,
                          Message 12 of 20 , Aug 15, 2003
                            From: "Casting Fool" <jester@...>
                            > "When you wish upon a bar, makes no difference where bubbles are. They
                            all go where atoms are, your dreams come truuuuuuuue!"

                            I'm sorry, Jiminy Cricket told me that my meter, and rhyme, were off...

                            "When you use those millibars, bubbles never show and mar. They all go
                            where atoms are, your dreams come truuuuuuuue!"

                            Now I'm gonna go step on a bug...

                            :O)

                            TTFN - Mike Jackson
                            Casting Fool & Son
                            Augusta, GA USA
                            http://www.cfnson.com
                          • Mike Brose
                            Jody..... pressure forces the air bubbles into solution (just like a soda pop bottle before you open it, you can not see the bubbles). If I m understanding you
                            Message 13 of 20 , Aug 15, 2003
                              Jody..... pressure forces the air bubbles into solution (just like a soda
                              pop bottle before you open it, you can not see the bubbles). If I'm
                              understanding you correctly, it will not create hollow castings. Just
                              like the soda pop analogy, you won't find a big bubble in the center of
                              the casting. For hollow castings, there's several ways:

                              Slush casting (kind of a misnomer as true slush casting is an absorption
                              process as is used for casting ceramic castings or hollow latex pieces):
                              rotating a mold by hand coating the inside of the mold evenly, until the
                              resin gels or nearly sets up. Two or three shots of resin may be
                              necessary to get the thickness you need. Trying to do too much in one
                              shot can create problems. Depends on the piece and the size of the
                              casting.

                              Rotocasting: same as slush casting, only done on a machine (I have a
                              Mannetron rotocasting machine which I like quite a bit). It rotates the
                              mold on two axis at the same time (you can set the speed of each frame to
                              get the inside of the mold to coat the way you want it). It is much more
                              precise than slush casting, with very consistent results (after you
                              figure out the best frame speeds for the resin you are using and the
                              piece you are casting). Creates some very nice hollow castings. The large
                              puppet hands, feet and torsos that I make are all rotocast. No pressure
                              needed!

                              Core molding: consists of an outer mold and a core (some call it a plug)
                              that goes on the inside of the outer mold. There is a space between the
                              core and the outer mold of a certain thickness, which will be the
                              thickness of the part cast.

                              For an enclosed hollow cast pieces, slush or rotocasting works best. For
                              an open hollow cast piece, e.g., like a car body, a core mold is usually
                              easiest.

                              You can pressure cast with a 3 minute resin. The mold just needs to be
                              set up so you can pour quickly and then get it in the pressure pot
                              reasonably quick too. If you have a good compressor, you can get the pot
                              pressurized very quickly. That's not really a problem. I do use some
                              longer set resins too. The Polytek 1512X (it's about a 5 min. resin) has
                              plenty of working time for certain pours that I do. BJB has some longer
                              setting resins that are nice (they have quite a few choices). I haven't
                              tried the Alumilite slow set resin yet.

                              Yes the longer set resins are a more relaxed pace, but there's drawbacks
                              to getting too long a set time. Demold times can be really way too long
                              on some of the longer setting resins. I've also found that some
                              manufacturer's longer setting resins work better or are of better quality
                              than others. I've found some more susceptible to shelf life or
                              contamination problems than their faster resin counterparts. In general,
                              at least for me, I use the shortest setting resin that I can that will
                              work for the project at hand. You can do some steps quicker than you
                              think you can with a little practice.

                              Cheers,

                              Mike Brose
                              www.puppetsandprops.com




                              On Sat, 16 Aug 2003 00:02:10 -0000 "dsbnumpsie" <dsbnumpsie@...>
                              writes:
                              > Hi folks, me again. Stop your groaning.. this won't hurt a bit, I
                              > promise.
                              >
                              > Anyway, I've read lots recently about casting under pressure.
                              > Through
                              > reading, reviewing and research I've learned that casting under
                              > pressure forces air bubbles to the centre of the casting. Does this
                              >
                              > mean that in effect you could create a hollow cavity in the casting,
                              >
                              > or is that just wishful thinking?
                              >
                              > Another thing I've wondered about is what the set time is with the
                              > resin you guys are using for pressure casting. Smooth Cast 320 has a
                              >
                              > 3 minute working time, and roughly a 10 minute set time. Would a
                              > fast
                              > curing resin like that be ok for pressure casting? Or is it more for
                              >
                              > the slower set resins? I'm wondering if a tank would come up to
                              > pressure fast enough for it to make a difference in a fast set
                              > resin.
                              >
                              > See, completely painless :)
                              >
                              > Jody
                              >
                              >
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                              >
                              >
                            • mwhirailer
                              Hi Jody, Nice try on hoping for a hollow cavity with pressure. 8^) To get a hollow casting you re looking for rotational casting. Remember the chocolate Easter
                              Message 14 of 20 , Aug 15, 2003
                                Hi Jody,

                                Nice try on hoping for a hollow cavity with pressure. 8^) To get a hollow casting you're looking for rotational casting. Remember the chocolate Easter Bunny analogy that I made a couple of weeks back? That's the epitome of rotational casting. In fact the Germans developed the technique specifically for candies in the 20's or 30's of last century. If you're interested in rotational casting take a look at www.mannetron.com and http://www.plastermaster.com/rotation/. These sites will give you a good idea of what you can do with this equipment.

                                Several list members have rotational machines and might be willing to do some castings for you if that's what you're looking to have done. They are not cheap machines.

                                You can also do hand held rotational molding by rolling the mold on an X and Y axis in your hands for the time that it takes the resin to cure. I can tell you from experience that this gets boring fast. Machines are the best way to go here as you get precise control over your inner and outer axis speeds.

                                As to pressure casting, I use a three minute pot life resin that works wonderfully with 40 PSI. For the 1/87 scale semi-tractor airdams that we're currently running, I'm setting my timers at 8 minutes. This gives the resin enough time to cure under pressure. Plus I start with a warm mold to accelerate curing once poured and pressurized.

                                Your resin will probably work out ok for pressure. I don't see where pressure would hurt the 300 series. You might want to check out other resins and manufacturers to see how their juice works against what you've already got.

                                Pressure works well with fast and slow resins. The key is how fast can YOU mix, pour, place in tank, clamp down, and pressurize the mold? It takes practice but you can actually get it all done with some molds and smaller tanks in under a minute. Our place was a whirlwind of activity this afternoon with a couple of jobs going through the paces and two casters trying to out-do the other with pressure casting using several small tanks.

                                I mentioned a large tank last week. This will be good for large molds. It will also be good for multiple molds using a slow set resin to sit under pressure for some time if not overnight. However, the larger the tank the slower it will fill. For example a 2.5 gallon tank like the ones from Sears, Harbor Freight, or the Alumilite tank will fill in a couple of seconds at 40 PSI if you let them. You can control the fill rate with a ball cock. I like to let my tanks fill slowly so as not to spill juice inside the vessel when using open faced or glove molds. But then there are times with a multi-part mold where I'll let'er rip as fast as she can.

                                One factor that comes into play with air tank fill rate is the regulator setting on the air supply. My compressor supplies 135 PSI. I usually regulate it around 95. This will have an effect on the speed with which the air travels through the hoses, valves, etc. If I regulate it up to 135, things will fill faster. It is very similar to a water faucet analogy. In fact when using the big tank, I'll up the regulator to 135 to get maximum movement from my compressor to the tank in order to fill it as quickly as possible. Hose and pipe diameter will also affect fill rate.

                                Another consideration is how the size of your air reservoir will come into play. Larger air reservoirs will contribute to faster fill rates. Horse power of your motor also affects the big picture. Some folks have 2.5HP 11 gallon compressors while others have 9HP 80 gallon or larger beasts. The smaller units are great if you've got one or two small pots. If you're using several different pots for production runs, then you need to consider bigger equipment. A friend of mine has a 15HP 120 gallon behemoth compressor that fills his 50 gallon tanks in no time. There are a lot of variables to consider in just equipment alone. Then you have to look at your juice.

                                Some resins take 8 or more hours to cure. Look at BJB Enterprises for a better idea on this. The point is that you can use just about any resin under pressure. Whether it's a 3, 10, 20 minute or 1 hour pot life most resins will perform well in this application.

                                Hope this helps,
                                Terry Wellman
                                St. Charles, IL

                                [Non-text portions of this message have been removed]
                              • appleblossomhollow
                                Hi. I m still new to the list. But I got such great tips on how to paint my resin, that I thought I would ask another question from you pros. I am wanting to
                                Message 15 of 20 , Nov 11, 2003
                                  Hi. I'm still new to the list. But I got such great tips on how to
                                  paint my resin, that I thought I would ask another question from you
                                  pros. I am wanting to cast clear resin. I am almost sure that I want
                                  it to be Smooth-On's Crystal Clear 200. It doesn't require post-heat
                                  curing like some of the other SmoothOn Crystal Clears. But it does
                                  require pressure casting, I think. I've been trying to figure out if
                                  I also need a vaccum chamber and pump for my silicone. I think
                                  someone said that I could pressurize my silicone, and that would
                                  enable my silicone mold to be pressure cast safely. I'm not sure if
                                  any of this is right. Plus, if any of you have any other
                                  recommendations for Clear casting resin or tips, please let me know.
                                  Again, thanks for all the help on the painting resin. These lists are
                                  so great, for us newbies.
                                  Ginger Chavez
                                • steveneserin@aol.com
                                  In a message dated 11/11/2003 21:18:47 GMT Standard Time, ... you can do both, either pressurizing or vacuming, its just to get rid of those little bubbles in
                                  Message 16 of 20 , Nov 11, 2003
                                    In a message dated 11/11/2003 21:18:47 GMT Standard Time,
                                    appleblossomhollow@... writes:

                                    > Hi. I'm still new to the list. But I got such great tips on how to
                                    > paint my resin, that I thought I would ask another question from you
                                    > pros. I am wanting to cast clear resin. I am almost sure that I want
                                    > it to be Smooth-On's Crystal Clear 200. It doesn't require post-heat
                                    > curing like some of the other SmoothOn Crystal Clears. But it does
                                    > require pressure casting, I think. I've been trying to figure out if
                                    > I also need a vaccum chamber and pump for my silicone. I think
                                    > someone said that I could pressurize my silicone, and that would
                                    > enable my silicone mold to be pressure cast safely. I'm not sure if
                                    > any of this is right. Plus, if any of you have any other
                                    > recommendations for Clear casting resin or tips, please let me know.
                                    > Again, thanks for all the help on the painting resin. These lists are
                                    > so great, for us newbies.
                                    >

                                    you can do both, either pressurizing or vacuming, its just to get rid of
                                    those little bubbles in the RTV so that the mold wont distort under pressure and
                                    so you dont get any anoying little balls of resin from where the resin has been
                                    forced into the tiny air spaces.

                                    just remember if you presurise you have to leave it pressureised for the
                                    entire cureing phase of your RTV... no takig it out early or the bubble will just
                                    reapear, pressure just makes them very small after all.

                                    if your master is hollow you should also look out.. as the pressure can
                                    sometimes collapse or distort the master while the mold is curing. if your master
                                    is solid then no probs...

                                    Im about to start looking for clear resins so would be grateful to hear your
                                    results, mine would be for miniature figures, I need one that wont discolour
                                    over time.

                                    Steve Eserin
                                    www.thefiguretrader.co.uk


                                    [Non-text portions of this message have been removed]
                                  • Sylvan Scale Models
                                    ... Hi. I m still new to the list. But I got such great tips on how to paint my resin, that I thought I would ask another question from you pros. I am wanting
                                    Message 17 of 20 , Nov 11, 2003
                                      -----

                                      Hi. I'm still new to the list. But I got such great tips on how to
                                      paint my resin, that I thought I would ask another question from you
                                      pros. I am wanting to cast clear resin. I am almost sure that I want
                                      it to be Smooth-On's Crystal Clear 200. It doesn't require post-heat
                                      curing like some of the other SmoothOn Crystal Clears. But it does
                                      require pressure casting, I think. I've been trying to figure out if
                                      I also need a vaccum chamber and pump for my silicone. I think
                                      someone said that I could pressurize my silicone, and that would
                                      enable my silicone mold to be pressure cast safely. I'm not sure if
                                      any of this is right. Plus, if any of you have any other
                                      recommendations for Clear casting resin or tips, please let me know.
                                      Again, thanks for all the help on the painting resin. These lists are
                                      so great, for us newbies.
                                      Ginger Chavez


                                      I'd like to add a some thoughts on the Crystal Clear 200. We used some of
                                      it a couple years ago on a small project. The one thing we discovered was
                                      that you REALLY need to wear plastic gloves when working with it and be sure
                                      to scrub your hands THOROUGHLY after use. I noticed that traces of it would
                                      get on your skin and if you touch your face it will cause your eyes to burn,
                                      even after washing up. Be VERY careful with it.
                                      We pressure cast it a 60PSI and had no problems with the castings. We did a
                                      two step pour since we were imbedding parts in the castings.

                                      Clare Gilbert
                                      Sylvan Scale Models
                                    • randall smith
                                      just checked ebay. guy i bought off of has another pressure pot for sale at 64 dollars brand new. same one i bought. thought i d say something. has a buy it
                                      Message 18 of 20 , Nov 12, 2003
                                        just checked ebay. guy i bought off of has another pressure pot for sale at
                                        64 dollars brand new. same one i bought. thought i'd say something. has a
                                        buy it now price.

                                        randall

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                                      • Elmer McKay
                                        Ginger, I believe the best results are obtained by vacuuming the RTV, and then casting the parts under pressure. That is what I do, as quite a few on this
                                        Message 19 of 20 , Nov 12, 2003
                                          Ginger,

                                          I believe the best results are obtained by vacuuming the RTV, and then
                                          casting the parts under pressure. That is what I do, as quite a few on
                                          this list. Making a mold under pressure is a new idea that has been
                                          brought up recently, but I don't think it is better than vacuum. The
                                          pressure equipment is not to bad, price wise, but vacuum equipment can be
                                          more costly. I was casting for two years before I took the step to vacuum
                                          and pressure.

                                          You will find that the SC-325 is more viscus than the
                                          Pour-A-Cast. However, resins tend to absorb moisture. When that happens,
                                          air bubbles will form seemingly for no reason at all. Use plastic cups and
                                          metal spatulas for mixing. I use an artist pallet knife and 3oz plastic
                                          bathroom cups. That plus casting under pressure keeps the bubbles out.

                                          Also, only color the part B resin. That way you can have different colors
                                          of part B and uncolored part A for use with all. I divide my resin down
                                          into quart and pint bottles. US Plastics is about as cheap as anyone for
                                          obtaining these.

                                          Elmer.

                                          At 03:00 PM 11/12/03, you wrote:
                                          > Date: Tue, 11 Nov 2003 21:10:08 -0000
                                          > From: "appleblossomhollow" <appleblossomhollow@...>
                                          >Subject: Pressure Casting
                                          >
                                          >Hi. I'm still new to the list. But I got such great tips on how to
                                          >paint my resin, that I thought I would ask another question from you
                                          >pros. I am wanting to cast clear resin. I am almost sure that I want
                                          >it to be Smooth-On's Crystal Clear 200. It doesn't require post-heat
                                          >curing like some of the other SmoothOn Crystal Clears. But it does
                                          >require pressure casting, I think. I've been trying to figure out if
                                          >I also need a vaccum chamber and pump for my silicone. I think
                                          >someone said that I could pressurize my silicone, and that would
                                          >enable my silicone mold to be pressure cast safely. I'm not sure if
                                          >any of this is right. Plus, if any of you have any other
                                          >recommendations for Clear casting resin or tips, please let me know.
                                          >Again, thanks for all the help on the painting resin. These lists are
                                          >so great, for us newbies.
                                          >Ginger Chavez
                                          >
                                          >


                                          =========================
                                          Elmer W. McKay
                                          Possum Valley Models
                                          http://www.ttscale.com/tsm.htm
                                          =========================
                                        • N Hill
                                          Hi all, Has anyone tried the flat bottom pressure pots available from C.A. Technologies - http://www.finishsystems.com/resincastingpressurepots.html - and if
                                          Message 20 of 20 , Jan 11, 2007
                                            Hi all,

                                            Has anyone tried the flat bottom pressure pots available from C.A. Technologies - http://www.finishsystems.com/resincastingpressurepots.html - and if so what is your opinion?

                                            Regards,
                                            Carl

                                            Carl Hill - Gatehouse Candles & Molds
                                            http://www.gatehousecandles.com




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