DCG and Pits

Dutchelm05 · Post by **Dutchelm05** » Mon Mar 08, 2010 11:26 pm

I have been using a 250 bloom gelatin and I am noticing pits in the emulsion.
I inspect the plate carefully before shooting and I do not see them but that isn't to say they are not there.
Can some of you DCGers provide some insight as to what this can be?
I cook the gelatin only 20 or 30 minutes plus 10 more minutes for AmDi.
I melt it at 45C never higher than 50C
I double filter
I do not have the cleanest clean hood but as I said, I don't really see dust specs.
Is there something in the processing that can do it?
All of Rollison's paper say he does know but thinks it is glass cleaning and or cook time

Thanks for any comments,
Tony

dave battin · Post by **dave battin** » Tue Mar 09, 2010 12:33 am

i can only say that i have had these issues when i (think) have over heated the gelatin like above 100C for too long. a test would to keep every thing the same and use a new batch?

Dutchelm05 · Post by **Dutchelm05** » Tue Mar 09, 2010 3:25 pm

Right, thanks Dave.
Hope to make a new batch this weekend.

Tony

Ed Wesly · Post by **Ed Wesly** » Tue Mar 09, 2010 5:05 pm

If there is no adhesion to the glass I would also have to chime in it's the cleanliness. It has been noticed than when cleaning glass there is one side that is "squeakier" when rubbing, and we used to use that side when coating resist. Do you use a dishwasher to clean the glass?

Dutchelm05 · Post by **Dutchelm05** » Tue Mar 09, 2010 5:50 pm

Thanks Ed,

I first clean the glass with hot water and dish soap
Then I have a tank that has some micro 90 and a bit of bleach that has a filter and circulating water, it is heated at around 120F. I normally let it sit in there for a few days.
Then I rinse it in hot water and put them in another tank of warm DI water for hours or days.

When I remove the glass it is under my 3rd world flow hood and I make sure the water sheths off. Then it goes under a warm blower so it drys fast.

Tony

JohnFP · Post by **JohnFP** » Wed Mar 10, 2010 6:51 pm

I clean my plates with HydroChloric Acid (about 10% working solution). You can find this at Home Depot used to clean masonry work. I let is soak overnight, then use a plastic wool (not steel wool but plastic used for scrubbing teflon). Then scrub with the wooly under as hot water as I can take confortable. Then lay down on a paper towel. Before all the water evaporates I use a clean paper towel (the 1/2 sheet ones) to finalize the clean. My experience from cleaning house windows proves that with the tiny little bit of moisture on the glass, a paper towel can be used to get a really really clean surface.

I have alway wondered and did some testing on those two different surfaces but really found no difference.

Pits, if I understand correct is either from too high a cook (too long does not cause them). These are pits without centers, just that greenish-yellow pit. If you look closely and see a center to the pit, then that is an impurity. Could be from the gelatin or contamination with your mixing containers, or simply some dust that fell in the mixing container or plate.