[Fwd: Re: [PPLetterpress] Plate cracking]
- Hi Gerald, I still can't post, please post for me.
Here's an answer for this guy:
The short answer is that his plates were too dry, and were allowed to
The long answer: of the variable physical properties of photopolymer is its
moisture content. Exposing and baking the plates is all about affecting that
- and the plates do not loose their sensitivity to moisture after
processing. If a plate was exposed or baked for too long, it will be very
dry, if it isn't wrapped in plastic to hold what little moisture is left in
it, it will continue to loose moisture until it begins to curl, and then
crack (because its contracting faster than the steel is).
If a plate curls, but has not cracked yet, it can be soaked in water
again, until it's soft enough to flatten (which it may do by itself), a
brief dry (bake) and then another (short) post expose should make it like
Or it could be a strange temperature situation that affected the polymer one
way, and the steel the other - but since I've had this happen to me a number
of times - the moisture principle is what's more likely to be working in
When processing without machine (uncontolled, in other words) anything can
happen, so it would be nearly impossible to pin down what, in his process,
went wrong. I'd try to make sure water temperature, and baking temperatures
are not too high, and the time limits are not being exceeded, then I'd wrap
those plates in platic right after processing. Platic wrap comes in many
different forms - not all trap moistre (Saran brand is the only one I've
found to work).
I hope that helps.
Em Press - New Bedford, MA
> From: "Gerald Lange" <bieler@...>
> Reply-To: PPLetterpress@yahoogroups.com
> Date: Fri, 11 Jul 2003 18:27:41 -0000
> To: PPLetterpress@yahoogroups.com
> Subject: [PPLetterpress] Plate cracking
> A fellow called me up the other day regarding his plates cracking and
> wondered if I knew the reason. He exposed these with a "light box" and
> washed them out by hand in the "bathtub." He made about nine of them
> and they all cracked the next day. These were "thick" steel-backed
> I could make some guesses but have no real clue as to what the problem
> is. Anyone else ever experience this?