Martin
I just coated plates with your gelatin and FAO in the same proportions:
30 gms gelatin
6 gms FAO
300 mls water
3 drops of Kodak Photoflo
Will shoot same as before and see if the gelatin makes any difference. As always, I'll post results here.
Martin tests 2
Martin tests 2
OK, thanks a lot.Dinesh wrote:Martin
I just coated plates with your gelatin and FAO in the same proportions:
30 gms gelatin
6 gms FAO
300 mls water
3 drops of Kodak Photoflo
Will shoot same as before and see if the gelatin makes any difference. As always, I'll post results here.
If you illuminate the FAO/gelatin layer with your 457nm laser, do you notice any significant light absorption?
Martin tests 2
I'll check for this.Martin wrote:If you illuminate the FAO/gelatin layer with your 457nm laser, do you notice any significant light absorption?
Martin tests 2
So, 10 plates exposed at 2.2mW. Develop:
10 secs in 1% hydrogen peroxide
5 min in running water
dry in IPA as per standard dcg
Absorption:
Reading before plate (ie the ref) = 1.86
Reading after plate = 1.80
Hence absorption = (1.86 - 1.80)/1.86 ~ 3.2%
No change in sensitivity due to softer gelatin. However, the plates had a white haze, presumably due to the softer gelatin (I did not fix, since I was trying to reproduce the original procedure). Good exposures were attained at roughly 300 mJ. However, I increased the percentage of peroxide to 2% and got significantly better results. The 300mJ exposure was noticeably brighter after processing in the increased peroxide concentration.
10 secs in 1% hydrogen peroxide
5 min in running water
dry in IPA as per standard dcg
Absorption:
Reading before plate (ie the ref) = 1.86
Reading after plate = 1.80
Hence absorption = (1.86 - 1.80)/1.86 ~ 3.2%
No change in sensitivity due to softer gelatin. However, the plates had a white haze, presumably due to the softer gelatin (I did not fix, since I was trying to reproduce the original procedure). Good exposures were attained at roughly 300 mJ. However, I increased the percentage of peroxide to 2% and got significantly better results. The 300mJ exposure was noticeably brighter after processing in the increased peroxide concentration.
Martin tests 2
That doesn't look like huge absorption. I guess at 405nm I may have had 20% or so.Dinesh wrote:Absorption:
Reading before plate (ie the ref) = 1.86
Reading after plate = 1.80
Hence absorption = (1.86 - 1.80)/1.86 ~ 3.2%
How much light do your standard DCG plates absorb at 457nm?
Assuming you cannot increase FAO concentration much further, switching to another ferric salt might become a serious option. My blue LUMILED - still waiting for a nice blue laser...- indicates far better absorption for FAC (ferric ammonium citrate) than FAO.
So far the good news. I'm not particularly impressed with the 300mJ though (at 405nm I might have exposed the plates at 1 - 5mJ - occasionally 0.5mJ only).No change in sensitivity due to softer gelatin. However, the plates had a white haze, presumably due to the softer gelatin (I did not fix, since I was trying to reproduce the original procedure). Good exposures were attained at roughly 300 mJ. However, I increased the percentage of peroxide to 2% and got significantly better results. The 300mJ exposure was noticeably brighter after processing in the increased peroxide concentration.
Martin tests 2
Well, I put in 6gms of FAO in 300 mls water, as per the original instructions. I can presumably load more FAO into it. In fact, I was going to try doubling the FAO concentration next. I assume that there will be a point when the FAO will saturate, but 6 gms dissolved very quickly. Also, I forgot to mention that I put in 3 drops of Kodak Photoflo; you mentioned that this was an essential part of the formulation. Yes, 300 mJ is not very good, but it may get better with increased FAO. By the way, what if I mix the FAO with FAC?Martin wrote:Assuming you cannot increase FAO concentration much further
You know, I never measured this! Anyway, here's an illustration from "Topics in Applied Physics", vol 20 "Holographic Recording Materials" ed H. M. Smith. The illustration itself is taken from papers by Shankoff* and B. O'Brian**Martin wrote:How much light do your standard DCG plates absorb at 457nm?
*T. A. Shankoff: "Applied Optics" 7, pp 2101 (1968)
**B. O"brian: "J. Opt. Soc. Am. 42, p. 101 (1952)
Martin tests 2
Good. Let's see if you'll get some significant absorption from your blue laser. You might simply verify that with a FAO solution without adding any gelatin...Dinesh wrote:Well, I put in 6gms of FAO in 300 mls water, as per the original instructions. I can presumably load more FAO into it.Martin wrote:Assuming you cannot increase FAO concentration much further
Yes, I remember having heard photo people say, gelatin could take much more FAO than dichromate - maybe up to 3x the quantity of dichromates.In fact, I was going to try doubling the FAO concentration next. I assume that there will be a point when the FAO will saturate, but 6 gms dissolved very quickly.
Right - actually my surfactant was Triton-100.Also, I forgot to mention that I put in 3 drops of Kodak Photoflo;
Yes, that might be worth a try.Yes, 300 mJ is not very good, but it may get better with increased FAO. By the way, what if I mix the FAO with FAC?
On the other hand, I now really wonder if FAC wouldn't be more appropriate to blue recordings. Photographic wisdom used to claim far better speed for FAO than FAC. But then, wasn't that essentially based on broadband UV exposures?
FAC has some benefits: it's much less toxic. Hence it's easier to purchase than FAO (by the way, you'd have to look for the green stuff, not the brown one).
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[quote="Martin"]How much light do your standard DCG plates absorb at 457nm?[/quote]
You know, I never measured this!
I see - thanks for reminding me of Shankoff. So how does your ammonium dichromate solution look like under your blue laser (and how does it compare with FAO or FAC solutions)?