I remember reading somewhere that formaldehyde could be used at 0.1 % of gelatin mass. Right?
For 16 grams of gelatin, that would make 16 mg of formaldehyde, that is, 43 milligrams of 37% formalin solution. Is it really this little?
Does the same figure work with glyoxal?
And, finally, if I can't find formalin tomorrow, can I try replacing it with Jobo E6 Stabilizer/final rinse (it includes formalin)? -- or do you know that the wetting agent would be a problem? The 250 ml concentrate makes 5 l of stabilizer, so the concentrate has quite a high formalin content. I could calculate the formalin concentration by comparing to E6 stabilizer recipe.
Well, I use 0.5 ml of 4% glyoxal (that is commercial 40% diluted to 4%) in every batch of 100 ml - 200 ml of 10% gelatin. This is the usual range. For chrome alum, I use the same 0.5 ml, but it is a 10% solution. Hardening is good enough for processing in about 24 - 48 hours.
E6 stabilzer that is currently on the market made by Kodak does not have formalin and the photo flo present will mess with the coatability. Other companies make a stabilzer with formalin and it would work, but again the photo flo (surfactant) will affect coatability. The only answer is to try it out.
Failure :( :( :(
Now we tried it out. The one half that was digested in room temperature (no hypo sensitizing) and coated two days ago. Dmin is very low (no fog), that's good, but... It seems something like 0.01 ISO and Dmax is maybe about Dmin+0.1 so very very low contrast. We exposed a 6x6 frame at f/2.8 20 seconds in bright sunlight, no visible image at all. Just clear film. With enlarger we could get some darkening but contrast is very very low.
The second problem was that emulsion loosened. We couldn't get formalin or chrome alum, and E6 stabilizer didn't harden it . But our emulsion was hard enough that it survived the process even when it loosened. Maybe we need a subbing layer or different support material... Or wait more to allow it dry better. (EDIT: Or, can bad noodle washing be a reason too? This was the first batch we washed only about 20 minutes and noodles were over 5mm thick.)
But, our coating seemed quite consistent and good.
We used XTOL 1+1 as developer, then we made a cocktail (added some hydroquinone and rodinal to it) to try to increase contrast...
Now, when we get some hardening stuff, we will coat the hypo-sensitized emulsion. I really hope that it shows more contrast and better ISO...
We didn't really get any image at all now.
I have some ideas, like:
- This food gelatin is very inactive and sulfur sensitization is really needed, which would explain very low ISO and very low contrast
- Our emulsion is not thick enough, thus low DMAX? (It seems good to me, but...)
- Our developer cocktail may have some restrainer to control fog with real films? Maybe we should use metol-HQ paper developer (Dektol?) to get better contrast?
And some questions:
- Can noodle washing wash silver halides away?
- Can remaining ammonia affect the results?
- Anything else that comes to mind??
Last edited by hrst; 09-21-2009 at 01:08 PM. Click to view previous post history.
Sulfur or sulfur + gold will raise speed and contrast.
I can't help you out with food grade pig gelatin. Not enough information.
I use Dektol 1:3 for 3 + minutes or D-76 for 11 minutes.
Sorry I cannot be of more help.
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Oh yeah, made a new coating with sulfur-sensitized stuff and adjusted the blade gap to make a thicker coating. The problem really was too thin emulsion, I think:
We were afraid of too thick emulsion because of too low gelatin at first (which made coating thick difficult) and because of huge weight of the wet emulsion. But of course it loses water when it dries and starts to resemble normal film! The first coatings indeed were almost transparent even before processing.
Not tested the ISO yet (we let it dry first) but now the Dmax seems something like 2.0 rather than 0.1! Maybe the sulfur sensization helped too but with this coating I really see the difference between thin (very low Dmax) and thick emulsion. Now the fully fogged test strips also develop faster to Dmax, 20 seconds in Dektol 1+2 rather than 2-3 minutes. Sulphur?
Oh la la!
I'll post the results...
- OHP film, not for laser but for hand-writing (smooth unlike the laser films).
How coating was done?
- We made a blade that resembles PE's blade a little. Not so good, I guess, because PE's put a lot of effort but ours is just one day's work, but seems to work for us, for now. It has two 2x2x10 cm stainless steel sticks that are heavy to keep it stable and a thin stainless blade (polished carefully, finished with aluminum oxide polishing) between them, mounted with screws so the gap can be adjusted.
Last edited by hrst; 09-22-2009 at 06:48 PM. Click to view previous post history.
Any film intended for use in digital printing is probably going to cause problems. The mordant in the coated side can be a real pain and absorb the wrong things.
Yeah. I actually bought these OHP films to use them as animation cels (that's an another interest of mine ) -- tracing the line art and them painting them in acrylic, and then film them in 16mm. I built an animation stand for that. That launched my interest in motion picture film, MP film processing, film processing in general and that way I was suddenly interested in making some film. Now I've almost forgotten the animation :rolleyes:...
Overhead projector films you can get from most sellers are for laser printers (less expensive) or for inkjet printers (much more expensive). Both of them have a special surface that helps the toner or ink to adhere, and, in addition, they discolor in no time. The mat surface lowered the contrast too much for animation camera work so I had to find a cheap alternative with no surface treatment.
It took some effort to find these traditional, cheap "hand-writing" films with unprocessed surface. But it's probably not acetate, it's harder (like polyester). If they are really polyester, I'm lucky.
One source for cellulose triacetate sheets could be Chroma Colour. They sell animation cels that are triacetate:
Yeah, now it works. Problem was way too thin coating. Now we get the same speed, about ISO 10, with all three emulsions with different hypo content, probably because we forgot the heat treatment after adding the hypo (it was just 2-3 min at ~40C). Fog is low and Dmax is high, contrast seems very good. I'm very happy about this emulsion!
But, the emulsion doesn't adhere to film base. It loosens in processing or even before. We have no hardening yet because we couldn't find a quick source for formalin, glyoxal or chrome alum but I think that's not the only problem. Maybe we need a better base or a subbing layer.
I attached an example. I dropped this one on floor (emulsion down, of course!) before exposure, that explains the white dust . Emulsion was loosened as you can see. But, the contrast and speed are OK! This one is in fact the not hypo sensitized one.
Big thanks PE and Ray for tips!
Last edited by hrst; 09-23-2009 at 06:33 PM. Click to view previous post history.
Congratulations. Looks better than some of mine!
Do you have any speed estimate compared to paper or film?