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A few carbon basics

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  • DAVID REID
    Dean, Os, et al, For your information a quick summary is as follows: High Activity: A fairly high Iodine adsorption or Methylene Blue adsorption factor (so
    Message 1 of 1 , Apr 29, 2000
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      Dean, Os, et al,
      For your information a quick summary is as follows:
      High Activity: A fairly high Iodine adsorption or Methylene Blue adsorption factor (so should work well)
      It is this count that measures the activity of the carbon and is a good indication of how well it will work. This type is genarally good for finishing or filtering as well.
      Primary: Normally a finer grade for primary treatment (can be powder or fine granulated). More commonly sold in the extruded form as a lot of people are a bit lasy and dont want to clean everything properly. In this form it quicky settles and sits in the bottom of the container so may not neccesssarily do as good a job although it should be good at removing the fusils which tend to settle towards the bottom anyway. I personally prefer the powder form as it disperses very well throughout the alcohol although it makes it look very black and you then have to do a good job of filtering the final product. This way you know it has done its job. The other way with just the extruded form you really need to agitate the alcohol daily or at least once a week. To cover my bases I use a bit of each and my alcohol as a result tastes really good. Used this method to clear up some of my earlier alcohol that wasnt too brilliant and after 6 weeks on treatment you couldnt tell the difference. There wasnt anything wrong with the alcohol initially, as it will not fix that, just that it hadnt been distilled as well as I do now and contained a few more impurities that proper reflux would have left behind. Unfortunately a lot of people dont like the powder method as it does tend to leave a black scum which means more cleaning up but if you do it when you empty the container I find it is very easy.
      As a rule the longer you can leave it on carbon treatment the better it will do its job and the better the alcohol tastes. You will also find you can reduce the amount you use as well.  A good primary will also be fairly broad spectrum and as well as polishing and deodorising will remove reactive organics (aldehydes and aminos (building blocks of protein still left in the spirit) and most importantly absorbing potentially poisonous higher alcohols (the fusil oils). Getting rid of the more harmful impurities hastens the maturing of the alcohol letting the good esters you want estify quicker. Sometimes when a carbon dosnt do as good a job as it should it is because the spectrum it will range over is too narrow. In other words the micropore and mesopore sizes are too narrowly defined. This is where mixing a couple of carbons of different range can help. The grades that are generally recognized as good for alcohol treatment are 8 x 30, 12 x 40 and .25 to 2.5mm.
      CR = Contact Reactive and generally good for removing reactive organics. Finer than Primary and normally sold in the extruded form.
      Reflux: Quite often chosen on pore size and if it does not have a wide enough range sometimes not so brilliant. Because a properly refluxed product will generally contain less contaminants the pore size chosen is sometimes a bit smaller than normally.
      Both Contact Reactive and Reflux carbons  differ from the others in that they tend to combine the two processes of treatment and filtering allowing people to spend less time on treatment in theory but in practice it dosnt tend to work as well as you would hope and the reality is if you want to get superior spirit the longer you can leave it on carbon treatment the better. Anything up to 6 weeks or even 2 months is totally acceptable although again most of the work is done in the first week. I personally dont use a lot of carbon as I try to distill at a greater purity initially but I also dont like to see any treatment under a week. I know some of the books say you can use 2 days but to me this is far too short. Some of the spirit that I have tasted that has been treated for this short a period still tends to have a bit of the rawness of fresh spirit to me.   
      Finishing or Filter Carbon: This generally has some of the best Iodine absorption of the lot and are what you should use in your final filtering or polishing of the spirit. You should be very careful that the carbon does not flow through this too fast (ideally about one drip a second) as any good it does can be quickly undone by insufficient treatment.
       
      Activated carbons are all active when they are manufactured but to remain active they must be kept in a airtight and moistureproof container or sack ( normally sealed plastic or very heavy cellophane type bags overseas) so they cannot react with oxygen or absorb moisture as this quickly reduces their ability. If buying activated carbon I suggest you put it in plastic jar (without a lot of headspace if you open it regularly) with a good sealable lid. Sometimes when you buy carbon and it dosnt work properly it is because somewhere in its journey it has been open to the air and moisture. To ensure I now get fresh carbon when I first open a bag I take out what I need and immediately split the rest up into various sized portions that I am likely to need putting these into the required container and then srewing or sealing the lid down tightly.
      B.r.,  David
       
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