A few days ago I received some DAS from Phototypie.fr
Went ahead and poured some tissues for testing yesterday; this morning the first ones were dry so I could do an initial test. Well, that's not going so well. There are MASSIVE problems with poor tissue adhesion and bubbles. Here's an example:
For scale: the test strip is ca. 2.5" wide.
Details:
Glop recipe for 100ml:
Gelatin: 10g
Pbk7 pigment, aqueous dispersion: 0.1g
Sugar: 3g
Glycerin: ca. 0.2g
DAS (diazostilbene): 0.4g
Tissue poured onto Yupo to a weight height of 0.8 ~ 1.0mm.
The DAS was weighed out and added as a solution in 10ml warm water to the warm glop under red safelight.
Tissues were dried in the dark.
Exposure of the test strip above was 12 minutes for the darkest patch on the right, exposed at 2 minute increments, under a strong 400nm UV light.
After exposure a very clear print-out image is seen for the darkest patches on the dry tissue. Printout image extends further into the weaker patches upon soaking the tissue.
Tissue soaked in tap water (<<20C) for 2 minutes. Millions of bubbles appear. I wiped them off the tissue surface (under water) just before mating with Yupo final support.
Sandwich was allowed to rest for ca. 10-15 minutes. Development in lukewarm water, ca. 41C. After peeling the temporary support away (ca. 4 minutes into development), the lightest patches are still visible, but these wash away pretty soon. The darkest patches immediately show massive bubbles/blisters and many bubbles still present. The lightest patches show no bubbles, but do not adhere well. Note the left-most patch in the example above with partial adhesion.
I re-read the section in King, Nelson & Lockhart on diazo sensitizers and I think I should be doing everything pretty much correctly. The amount of DAS sensitizer is the same as the one listed in the DAS formula on page 135. Otherwise I would suspect that the amount of DAS was below the 'critical mass' mentioned on page 134...if not for the fact that it shouldn't be; I'm right at the 1:25 DAS:gelatin ratio that King et al. recommend as a mininum.
I took a tiny bit of DAS from the container (under red safelight) and examined it under regular room light; it's a dark pink color. Upon exposure to strong UV it darkens to a very deep red, nearly black color. A weak solution of the powder is nearly colorless with a slight tinge of yellow, but turns distinctly yellow upon exposure to UV. Since this is my first experience with DAS, I don't know what the stuff is supposed to look like, but it seems to roughly match the descriptions I've been able to find.
Does the problem ring a bell with anyone who has used DAS before?
With ammonium dichromate I can get perfect transfers every time with the process outlined above, so I'm aware of the basics.
Went ahead and poured some tissues for testing yesterday; this morning the first ones were dry so I could do an initial test. Well, that's not going so well. There are MASSIVE problems with poor tissue adhesion and bubbles. Here's an example:
For scale: the test strip is ca. 2.5" wide.
Details:
Glop recipe for 100ml:
Gelatin: 10g
Pbk7 pigment, aqueous dispersion: 0.1g
Sugar: 3g
Glycerin: ca. 0.2g
DAS (diazostilbene): 0.4g
Tissue poured onto Yupo to a weight height of 0.8 ~ 1.0mm.
The DAS was weighed out and added as a solution in 10ml warm water to the warm glop under red safelight.
Tissues were dried in the dark.
Exposure of the test strip above was 12 minutes for the darkest patch on the right, exposed at 2 minute increments, under a strong 400nm UV light.
After exposure a very clear print-out image is seen for the darkest patches on the dry tissue. Printout image extends further into the weaker patches upon soaking the tissue.
Tissue soaked in tap water (<<20C) for 2 minutes. Millions of bubbles appear. I wiped them off the tissue surface (under water) just before mating with Yupo final support.
Sandwich was allowed to rest for ca. 10-15 minutes. Development in lukewarm water, ca. 41C. After peeling the temporary support away (ca. 4 minutes into development), the lightest patches are still visible, but these wash away pretty soon. The darkest patches immediately show massive bubbles/blisters and many bubbles still present. The lightest patches show no bubbles, but do not adhere well. Note the left-most patch in the example above with partial adhesion.
I re-read the section in King, Nelson & Lockhart on diazo sensitizers and I think I should be doing everything pretty much correctly. The amount of DAS sensitizer is the same as the one listed in the DAS formula on page 135. Otherwise I would suspect that the amount of DAS was below the 'critical mass' mentioned on page 134...if not for the fact that it shouldn't be; I'm right at the 1:25 DAS:gelatin ratio that King et al. recommend as a mininum.
I took a tiny bit of DAS from the container (under red safelight) and examined it under regular room light; it's a dark pink color. Upon exposure to strong UV it darkens to a very deep red, nearly black color. A weak solution of the powder is nearly colorless with a slight tinge of yellow, but turns distinctly yellow upon exposure to UV. Since this is my first experience with DAS, I don't know what the stuff is supposed to look like, but it seems to roughly match the descriptions I've been able to find.
Does the problem ring a bell with anyone who has used DAS before?
With ammonium dichromate I can get perfect transfers every time with the process outlined above, so I'm aware of the basics.