Crystallization problems w/ Dip-n-shoot or G307

[Joe Farina]

I've had some crystallization problems with G307. It may be due to the cool temp of 16C (60F) used when drying. When immersing the gelatin layer in the 5% solution of potassium dichromate (with a little glycerol and Photo-flo), it comes out clear, but after drying a while, white crystals form, especially around the edges (where the coating is thin) but also sometimes as spots in the middle of the plate. My gelatin concentration is about 13%.

Dave made a post a long time ago (it may have been in relation to his Dip-n-shoot method, which is similar to G307) where he mentioned that raising the drying temp took care of the crystallization issue:

https://www.holographyforum.org/forum/v ... als#p49738

I'm wondering if anyone else had the same problem.

[Manul]

According to the link, Jeff writes that this problem is related to the isoelectric point, which is quite reasonable. Do you use gelatin type A or B? There shouldn't be a problem with Type A.

If B, you can try adding a little TEA so that the pH becomes 6-7. I don't know what the result will be, photosensitivity may increase, maybe nothing will work.

[holomaker]

From what I remember, I had to drop the amount of amdi in the sensitizing bath and also added a bit of soap. I was shooting in green back then so wanted as much dichromate in the film as possible. If your using blue light should work w out crystals , dilute your sensitizing bath a bit..

[Joe Farina]

Thanks Dave, that makes good sense. Part of my problem was over-loading the emulsion with dichromate when exposing at 488nm, as you suggested. I watched the plate as it was being exposed and saw a huge amount of scatter coming off the emulsion (it looked a little like frosted glass) when being exposed at 488nm. It worked fine at 532nm, but not at 488. I'm working on a different approach now (not G307). I guess Dip-n-shoot (and maybe G307) would be fine if the dichromate is kept at a low level (when used with blue light).