Somehow you have got to have the material all gelled to start with and then able to be made even more gelled in the light struck anti-nodes so that their refractive index is greater than in the lightly gelled nodes… .….as demoed beautifully in DCG.
What if you were to expose the entirety of the photopolymer to the expanded laser beam for a period of time right before the exposure? My thinking is that this would partially gel the photopolymer and allow reflection holograms to be recorded more effectively.
Yes, that's something to try also. I think it has been done in the early days of holographic photopolymers.
I'd fear though that it would come at the expense of photo speed and DE.
dannybee wrote: ↑Tue Jul 24, 2018 12:04 pm
also I know in many old photographic 1880 they use Glycerin with gelation, I made a gel plate for my wife to use in her card making it was gel & gelation. also I think all 3 could work together . one time I took glycerin (that had a fragrance add)and add it to gelation and it became almost like a cling vinyl sheet. just some ideas
I seem to remember that I never managed to get a hologram from an acrylamide-glycerol-gelatin system. I guess glycerol in excess largely prevents (free radical) polymerization.
Got MBA and acrylamide, preparing to make my first batch with photopolymer. Found few recipes, going to try that one: MBA+TEA+Acrylamide+dye+PVA. Problem is all of these recipes have very different concetrations and recomendations for PVA selection (well, i have only 17-88 one, so not so hard now). Not sure how much MBA to put in those, one says ~0.4%, other says 0.6%, third says 1%. Same for acrylamide and TEA. And no really useful info about how it affects results. Any ideas?
Also, how to cover plates with PVA? Molding is out of question as i understand, PVA won't gelate in fridge i guess. Veil coating isn't really good for small plates and loses of emulsion are big because it sticks to trays. Mayer bar? Or just add some gelatine and do mold coating still? I've seen some recipes with gelatine+MBA, so i'll get kinda double-kind polymerization thingie?
Probably the most advanced work on PVA-AAM-MBA-TEA-dye has been done by the research groups in Dublin and Alicante. You can easily find their patents. E.g. look for "Suzanne Martin" + "photopolymer" + "hologram".
Note that both groups attempted to replace acrylamide with less toxic monomers.
As for coating PVA on glass, I havent't had much experience with PVA (tricky!). The easiest method used to be based on gravity settling.
Martin wrote: ↑Sun Jul 07, 2019 9:04 am
Probably the most advanced work on PVA-AAM-MBA-TEA-dye has been done by the research groups in Dublin and Alicante. You can easily find their patents. E.g. look for "Suzanne Martin" + "photopolymer" + "hologram".
Note that both groups attempted to replace acrylamide with less toxic monomers.
Thanks, made brief look on these, seems interesting. Have to figure out what went wrong, my polymer got massive crystallization on glass, most of layer is covered with rimes. Although got weak coins reflections on some slides, at least it has some sensitivity. Well, was hoping for at least less efforts than with FEG for some results, but seems it could be even harder.
Martin wrote: ↑Sun Jul 07, 2019 9:04 am
As for coating PVA on glass, I havent't had much experience with PVA (tricky!). The easiest method used to be based on gravity settling.
My solution (couldn't make 10% PVA as some of it didn't get dissolved, i think about 5-7%) has quite low viscosity (lower than 10% gelatine for sure) and does provide only very thin layers. I wonder if there is a way to make it more dense for veil coating.
Just got my mind blown. All photopolymers recipes contain monomers. But when i did experiment with PVA (polyvinyl alcohol)+speedball diazo sensitizer - it had no monomer, it was listed in the speedball emulsion datasheet (vinyl acetate) and i didn't use the emulsion, just pure PVA. But the mix has UV-light sensitivity still as i've got coins reflections on the layer. That means my PVA has some leftovers of monomer (vinyl alcohol?) or it just did polymerized faster, so water washed out less-polymerized PVA?
So you did try PVA (PVOH) + "Speedball diazo sensitizer, right? And, if I'm not misled, "Speedball diazo sensitizer" consists of the diazo stuff only (in form of a powder I assume), correct? In other words, this stuff is not identical with the "Speedball emulsion" (which is a liquid based on vinyl acetate + diazo), right?
If that's the case, you're dealing with a DIAZO but not with a photopolymer system. That said, it sounds interesting - particularly if speed is OK and holograms can be recorded. You might try to contact copy a transmission grating to see if resolution is fit for holography. You then could try gelatin instead of PVA...
Martin wrote: ↑Thu Jul 11, 2019 8:58 am
So you did try PVA (PVOH) + "Speedball diazo sensitizer, right? And, if I'm not misled, "Speedball diazo sensitizer" consists of the diazo stuff only (in form of a powder I assume), correct? In other words, this stuff is not identical with the "Speedball emulsion" (which is a liquid based on vinyl acetate + diazo), right?
If that's the case, you're dealing with a DIAZO but not with a photopolymer system. That said, it sounds interesting - particularly if speed is OK and holograms can be recorded. You might try to contact copy a transmission grating to see if resolution is fit for holography. You then could try gelatin instead of PVA...
Yep, just polivinyl alcohol (well, at least it says so on bag with it, 98% or so). The speedball stuff comes in two cans - speedball emulsion (listed with vinyl acetate in MSDS, about 700 ml) and the sensitizer bottle (there is about 2g concetrated sensitizer which i've dissolved in water as in instruction), i've used just the sensitizer to sensitize the polivinyl alcohol solution. The layer was quite thin but very foggy (seems very concetrated dye/particles or something) and blocked much of light. No holographic stuff (tried to do reflection one) but i've got coins reflections and pva-free areas in shadows. I did that few weeks ago, perhaps i should try again with smaller concetration of the sensitizer and with transmission copy.
The speed was ok, comparable with my FEG experiments (with 405nm laser). It's a bit confusing as was supposed to be used with monomer (vinyl acetate in the emulsion can) but works without too. May be that was because PVA didn't get fully polymerized (not fully dried perhaps) and got washed off by water in non-exposed areas.
vasimv wrote: ↑Thu Jul 11, 2019 9:13 am
perhaps i should try again with smaller concetration of the sensitizer and with transmission copy.
Yes, that would be interesting.
The speed was ok, comparable with my FEG experiments (with 405nm laser). It's a bit confusing as was supposed to be used with monomer (vinyl acetate in the emulsion can) but works without too. May be that was because PVA didn't get fully polymerized (not fully dried perhaps) and got washed off by water in non-exposed areas.
It looks like some diazos can actually crosslink colloids like PVA, gelatin etc. very much like dichromates. The D.A.S. I mentioned earlier acted like that. But it was difficult to get a sufficient amount of D.A.S. into the gelatin. That's why 405nm absorption was pretty weak and hence speed was lower than for FEG or DCG. But maybe the Speedball thing is better in that respect...
After reducing amount of sensitizer i've obtained some weak diffraction patterns from PVA + speedball sensitizer with transmission hologram copy, but it is really bad quality - i barely see some edges of shiny objects. Looks promising still (i like its simple developing process - just few minutes in water) but need to find a way to bleach the emulsion after developing in water as it blocks light and suitable only for amplitude holograms. Later i'll try it with gelatine too.
My recipe: 50ml of ~6% PVA solution + about 1.5 ml of speedball sensitizer solution, 405nm laser and transmission hologram on litiholo film (removed from glass). Viscosity of my PVA solution is quite low and coating with mayer bar didn't make good layer as i didn't have good levelled surface to dry. Will try to evoporate some water from PVA solution to get suitable viscosity.
