Ferric ammonium oxalate tests

Dichromated Gelatin.
vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Sat Aug 03, 2019 1:24 pm

Martin wrote:
Sat Aug 03, 2019 8:47 am
I've encountered this kind of problem many times. I thought it was due to a defective coating or a layer of insufficient thickness.
I think it may be because easy to over/under-exposure FEG emulsion as it tends to get milkyness in underexposed and big UV-shift in overexposed areas. So, even small difference in thickness causes under/over exposure in different areas. I'll try to return to coating with rain-x to remove plexiglass layer which may cause that difference. Will add IPA bath to remove rain-x leftovers before dipping in fixer and FAC solutions.

Perhaps, i need more thick glasses, those 1mm microscope slides tend to bend during coating. :( Perhaps it is one of reasons why i can't get good holograms again - i've used 2mm glasses (from litiholo's plates with film removed) before but switched to 1mm slides later.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Mon Aug 26, 2019 10:01 am

Got some promising results with pre-hardened emulsion (12g gelatine, 0.3..0.5g potassium alum, 1..1.5g of FAC per 100ml of emulsion), holograms aren't great (mostly in deep-blue/near-UV area) but better than in my most attempts. With mayer bar (i've used 120um bar, perhaps too thick) i was able to make layer of the emulsion by heating everything (emulsion, glass, mayer bar itself) to 50..60C. Without such heating it is like gum-like substance and nearly impossible to do coating. I need more practice with the bar as coating isn't uniform still, perhaps is good idea to dilute the emulsion with more water.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Sun Sep 01, 2019 10:05 am

I've diluted pre-hardened emulsion by adding 50% water (so, now it is 12g gelatine, 0.3..5g potassium alum and 1g FAC per 150ml of emulsion), easier to do coating. Looks like the emulsion requires more thickness. Did test with 200um and 80um mayer bars, first one has some red-shift to be visible but not enough to be good, with 80um it gets shifted into UV. Sensitivity is very bad - 30+ minutes exposure with power about 10..20mw, not sure why. Looks like my FAC stock got damaged by temperature/humidity or something else as it is more brown than green now. :(

So far got this (200um bar), both photos are same hologram. First one is before additional red-shift with collagen, second is after (got some additional milkyness and coating damage but quite good still). Preparing test with mold coating (as it is more precise and controllable).
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Joe Farina
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Re: Ferric ammonium oxalate tests

Post by Joe Farina » Sun Sep 01, 2019 3:48 pm

Wow, nice hologram. Quite a red-shift if you're exposing at 405nm. I think this really proves the viability of the ferric system, at least with your environmental conditions. The collagen seems to be working well -- what concentration and soak time did you use? The end result looks clean, did you have any difficulty with the uniform removal of the collagen solution?

I wonder if post-exposure baking will have a positive effect. With my MBDCG, it's definitely part of my processing schedule. A long, low-temperature bake after exposure seems to enhance hardening in exposed areas, without having other adverse effects. It may be different with ferric compounds, but might be worth a try. I bake at 65C for two hours, immediately after exposure. In my case, this produces noxious fumes (not sure of the exact cause) but the ferric system may be better in this respect. I do the baking in a portable oven, in a separate shed.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Sun Sep 01, 2019 5:16 pm

Joe Farina wrote:
Sun Sep 01, 2019 3:48 pm
Wow, nice hologram. Quite a red-shift if you're exposing at 405nm. I think this really proves the viability of the ferric system, at least with your environmental conditions.
Yeah, it works better in my temperature than non-hardened FEG but no stable result still. I hope to get better with mold coated plates, hard to do uniform coating with mayer bar on small plates. It seems like thick pre-hardened emulsion does red-shift on its own, just have to figure out right thickness and exposure time. I've seen almost infra-red images with that - 200+ nm red-shift without anything.
Joe Farina wrote:
Sun Sep 01, 2019 3:48 pm
The collagen seems to be working well -- what concentration and soak time did you use? The end result looks clean, did you have any difficulty with the uniform removal of the collagen solution?
9 minutes in 5% collagen solution. I didn't do any removal, just wiped off backside with paper towel then used 75-91-99 IPA bathes. I guess, IPA solution will get contaminated after some time with that processing but doesn't look that is problem with low number of holograms processed. Worst problem is emulsion tends to peel off (like in upper-left corner - dots in areas where emulsion got removed) after that.

I've tried even replace water swelling with 2..4 minutes in same collagen solution right after developing (not during reprocessing). It works but shift is not great.
Joe Farina wrote:
Sun Sep 01, 2019 3:48 pm
I wonder if post-exposure baking will have a positive effect. With my MBDCG, it's definitely part of my processing schedule. A long, low-temperature bake after exposure seems to enhance hardening in exposed areas, without having other adverse effects. It may be different with ferric compounds, but might be worth a try. I bake at 65C for two hours, immediately after exposure. In my case, this produces noxious fumes (not sure of the exact cause) but the ferric system may be better in this respect. I do the baking in a portable oven, in a separate shed.
I'll try but don't think it'll improve anything. FEG emulsion gets hardened during developing, baking shouldn't have any positive effect but may cause Fe2 to oxidize back to Fe3 instead.

Joe Farina
Posts: 724
Joined: Wed Jan 07, 2015 2:10 pm

Re: Ferric ammonium oxalate tests

Post by Joe Farina » Sun Sep 01, 2019 5:53 pm

vasimv wrote:
Sun Sep 01, 2019 5:16 pm
Worst problem is emulsion tends to peel off (like in upper-left corner - dots in areas where emulsion got removed) after that.
Around 1999 or so, Jeff Blyth published his silver halide diffusion method (which I think he updated and improved since then). I think in one of his papers (about that time or later), he detailed his glass preparation method. The diffusion method required that the gelatin adhere strongly to the glass. This involved the use of the 3-aminopropyltriethoxysilane which I mentioned earlier. I use this method, and it works extremely well. It's part of my routine, and I don't omit it. Gelatin does not come off the glass when using it. I believe another name for the same thing is gamma-aminopropyltriethoxysilane. This stuff does not like water, either water vapor in the air, or any water present in the IPA used to dilute it. The IPA can have water content, but apparently this doesn't store well (the silane/IPA mixture). I guess this is the reason why it's recommended to mix it fresh, each day. All you need to do is mix the silane/IPA, rub it on the glass, and let it sit in the open air for a couple of hours (more or less).

The only problem is in finding the silane. Ebay has that rather costly large volume in a bottle ($200). But I think this same silane might be available from other sources, if some searching is done. I believe microscopists use it for some types of slide preparation, and microscope equipment suppliers might have smaller volumes at less cost (I seem to recall seeing this many years ago).

This is available from a glass-working supplier in the US:

https://www.hisglassworks.com/bond-and- ... -html.html

I'm don't think this is the best way to buy the silane, though, because it's pre-mixed, and any bit of moisture in the solvent used by the supplier will likely affect shelf life. It may be worth a try however.

Thanks for the info on the collagen.

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Sun Sep 01, 2019 9:05 pm

Joe Farina wrote:
Sun Sep 01, 2019 5:53 pm
Around 1999 or so, Jeff Blyth published his silver halide diffusion method (which I think he updated and improved since then). I think in one of his papers (about that time or later), he detailed his glass preparation method. The diffusion method required that the gelatin adhere strongly to the glass. This involved the use of the 3-aminopropyltriethoxysilane which I mentioned earlier.
Yeah, i've read your recommendations about silanization, but it kinda kills point of using non-toxic FEG method. :) I usually just add few drops of 10% soduium lauryl sulfate solution and it helps for gelatine and PVA emulsions enough to stay on the glass unless additional reprocessing with longer water exposure used.

I think, i've got confirmation that thick pre-hardened emulsion does quite big red-shift (up to +200nm) as it got to red colors on edges (close to mold's scotch layers). My latest attempt with mold of 7 layers scotch tape (about 230..260um wet thickness) looks like they could do stuff but something went wrong during coating. Defects in middle of plates is the place where i've poured the emulsion. I guess, it got cooled too fast to spread uniformly and pressure from cover glass wasn't good too. So, i have to dilute the emulsion further and/or to rethink my sandwiching method.
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Martin
Posts: 121
Joined: Sat Apr 04, 2015 2:36 am

Re: Ferric ammonium oxalate tests

Post by Martin » Tue Sep 03, 2019 9:56 am

vasimv wrote:
Sun Sep 01, 2019 9:05 pm

I usually just add few drops of 10% soduium lauryl sulfate solution and it helps for gelatine and PVA emulsions enough to stay on the glass unless additional reprocessing with longer water exposure used.
That's interesting. Usually surfactants are said to have a negative impact on layer adhesion (I never tried sodium lauryl sulfate though).

vasimv
Posts: 58
Joined: Tue Apr 23, 2019 2:16 am

Re: Ferric ammonium oxalate tests

Post by vasimv » Tue Sep 03, 2019 3:55 pm

Martin wrote:
Tue Sep 03, 2019 9:56 am
vasimv wrote:
Sun Sep 01, 2019 9:05 pm

I usually just add few drops of 10% soduium lauryl sulfate solution and it helps for gelatine and PVA emulsions enough to stay on the glass unless additional reprocessing with longer water exposure used.
That's interesting. Usually surfactants are said to have a negative impact on layer adhesion (I never tried sodium lauryl sulfate though).
I've read that recomendation in one of papers for better PVA based photopolymer adhesion. It sure did work for me, so i've tried on gelatine too. Looks like working, not much but enough for some weird emulsions (like TEA/TMG only) to stay on glass. Without SLS these tend to peel off glass much more at drying.

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