13733Re: [PPLetterpress] Trouble with newly made exposure unit
- Feb 3, 2014Use a greenhouse plastic sheet from a garden shop, these are designed to pass UV
wavelengths. Acrylic filters UV out and reflects it back to the light source.
Put a black surface under the plate, I recommend a low durometer lightly textured
black elastometer or a matte black opaque polycarbonate. Hard or soft is a personal
choice. I prefer flexible to hard for the back and glass next to the light source.
Actually I would recommend buying a ready made exposure blanket from a company
like Douthitt and a 1/4" glass to contact against. This will require a vacuum pump.
http://www.douthittcorp.com/Catalog/catalog.htm (See P. 34)MaiKätzchenDum loquimur, fugerit invida Aetas:
quam minimum credula postero!
Odes Book I
From: Michael Hurley <mephit@...>
Sent: Monday, February 3, 2014 2:42 PM
Subject: Re: [PPLetterpress] Trouble with newly made exposure unit
On Feb 3, 2014, at 1:15 PM, Peter Nevins <nevins.peter@...> wrote:
> white reflective surface below film and plates is gonna be a problem: stray light bouncing around is bound to blur the image.
> without a vacuum, it's only possible to achieve uniform pressure by placing the lights below the glass and weighting the film and plate down onto the glass image from the top. it's simply not possible to tape the image down in a way that keeps it flat to expose from above.
> you could (?) weigh down a piece of glass to press the plate and film together from the top, but it won't be as effective.
> 1 inch is too close to provide evenly diffused light: you're bound to get bands of more and less exposure.
> ok there, I'm done
I don’t have any direct experience with platemaking, but I have looked into building an exposure unit before. According to my research, the acrylic could be the problem. Acrylics are almost always very reflective to UV, unless specifically stated to be otherwise. This is a standard treatment given to acrylics (especially things like Lexan) to keep them from getting milky-colored as quickly when used as windows. Even the specialty acrylics that don’t have the anti-UV additives aren’t nearly as UV-transmissive as glass. Anyone have any direct experience with this?
Michael Hurley Titivilus Press
123 North Holmes St. titiviluspress@...
Memphis, TN 38111 (901) 831-7640
Yahoo Groups Links
<*> To visit your group on the web, go to:
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
(Yahoo! ID required)
<*> To change settings via email:
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo Groups is subject to:
- << Previous post in topic Next post in topic >>