yellow tinge after developing

[dimasd]

I have been making transmission holograms for 12 years with my high school physics class. This year all of the holgrams I have developed have no image and appear to have a yellow tinge. I'm using PFG-01 plates. The chemical I use to develop are:

Kodak D19 developer 156.6g/L
Stop Solution (actually glacial acetic this year) 16ml/L
Bleach 10 g potassium dichromate and 10 mL Concentrated sulfuric acid to one L of distilled water.

The only thing different this year are new plates (but they are still PFG-01) and new stop (my old one was thrown out during cleaning over the summer).

When completed the plate has a yellow tinge and no image which is why I think its the chemicals. Could the acid in the bleach be so old that it's too strong? Any suggestions what could cause this yellow tinge and no image?

[admin_jsfisher]

The classic pyrochrome bleach is 4 g potassium dichromate to 4mL sulfuric acid (or 12 g sodium bisulfate) to 1 l water. Your formula is 2.5 times stronger, so, yeah that might explain things. The excess KDC could account for the yellow, too.

[dimasd]

OK...diluted the bleach and now the yellow color is gone, but the only thing showing up is a green halo. I was experimenting with just a simply quarter. My LASER is mounted on absorbing material, my sand box is on "Sad" balls...could it my mirror be dirty? It looks clean, but maybe it's smudged and not exposing the plate correctly?

[dimasd]

Cleaned the mirror, cleaned the quarter...same green halo. Could a LASER get old and I need more exposure time? I've always done 2- 3 seconds as it's a 5 mW LASER.

[admin_jsfisher]

PFG-01 plates, right? Two or three seconds exposure seems short. With the smallest 63mm x 63mm plates, and modest beam spread I'd expect you to be in the 5 - 10 second range.

During development, do the plates darken significantly...to the point you can see the safe-light only dimly through them?

[BobH]

I'd recommend not using stop bath, as I can't think of anyone else using it since the '70s. A water wash for a minute after development is fine. Also, how do you mix your developer? The bags of D19 are not uniformly mixed. When one pours a portion of the contents out of the bag, there's no way to know the actual composition of the developer. It's better to mix the whole bag, and draw what you need from that. Or, mix it from formula and pure chemicals (the best way for freshness and small quantity use.

[dimasd]

Chemicals are fine now.....exposure still not as good as I'd like. Finally got a key to show up fairly well with 2 sec exposure (It's a pretty high powered LASER). Thanks for all the suggestions!

[Ed Wesly]

Should make an exposure test: http://edweslystudio.com/Pedagogy/TS/Te ... meset.html and that should solve the problem. It sounds like it could actually be overexposed if the plate is stained yellow and no image at all.