DCG on acetate

jsfisher · Post by **jsfisher** » Sat Dec 28, 2013 12:17 am

I tried something new (to me) today. I tried to coat dichromated gelatin onto acetate.

My glass test plates for DCG experiments had been a collection of large-format microscope slides (2"x3"). After several reuses of the plates, they become scratched and stained from all the cleaning. So, since I had a quantity of acetate sheets (from the good old days of overhead projectors and all that), I thought I'd see how that would work.

Using Scotch Magic Tape along the long edges of the acetate, I attached a sheet to a glass plate salvaged from an old scanner. I don't have a Meyer bar, so I improvised with a 3/8" threaded rod. I used a 1-30-300 DCG formula with a few drops of dish washer rinse additive for a wetting agent.

All in all, I think it went well. The rod worked better than I had hoped. My table was less level than I expected, so that caused problems. I was a little skimpy, too, on how much DCG a squirted onto the acetate before drawing it with the rod (and the not level table didn't help), so my total coverage came up a bit short, but all in all, I think it went well.

I made three sheets total. They are drying now. I wonder how well they will work....

More to follow.

/JSFisher
The World's Worst Holographer

jsfisher · Post by **jsfisher** » Sat Dec 28, 2013 6:34 pm

For the three samples, I used three different acetate products.

Staples cover stock -- gelatin pealed easily.
3M Write-on transparency film -- gelatin pealed, but not as easily.
Highland printer transparency sheet -- we'll see if it survives the development process.

I think, too, the threaded rod wasn't such a good idea. I'll try a smooth rod next (salvaged from an ink-jet printer) letting the two strips of Scotch tape (that hold the acetate sheet to the glass plate) serve as spacer between sheet and rod.

/JSFisher
The World's Worst Holographer

Joe Farina · Post by **Joe Farina** » Sun Dec 29, 2013 11:30 am

Is there some reason why you want to coat on plastic? I mean, why not just get some window glass and a glass cutter. Glass is the material of choice for DCG. The only plastic Rallison recommended was Aclar, since it has enough moisture resistance. I don't know if it's a thermoplastic material, perhaps in that case, the edges could be fused (to seal it).

Jeffrey Weil · Post by **Jeffrey Weil** » Sun Dec 29, 2013 11:44 am

The word acetate has become synonymous with plastics made from petrochemicals even though they are different. Graphix brand still makes real cellulose acetate. You can find it in art stores. If you run into that stuff don't bother trying it. Those kinds of acetate sheets absorbs water and will pucker if you try to coat onto it.

jsfisher · Post by **jsfisher** » Sun Dec 29, 2013 1:45 pm

Joe Farina wrote:Is there some reason why you want to coat on plastic? I mean, why not just get some window glass and a glass cutter. Glass is the material of choice for DCG. The only plastic Rallison recommended was Aclar, since it has enough moisture resistance. I don't know if it's a thermoplastic material, perhaps in that case, the edges could be fused (to seal it).

My interest in holography is as a hobby. Like any good hobby, it is a sink for lots of both money and time, time spent doing things and learning things of interest. At least for me, the end result of a quality hologram suitable for bragging rights and all that is less important than the process that gets to that result.

So, I play. And I happen to have 100 or so sheets of acetate that have no other purpose in life anymore.

Tony DCG · Post by **Tony DCG** » Mon Dec 30, 2013 10:16 am

I'm surprised if the acetate could withstand the swelling and shinking during the post develpment process. I would have guessed that the gel would shear off especially around the edges.
I heard of dark tales where even using thin glass is not strong enough to handle the shear strength

The World's Worst Holographer could be the most interesrting man in the world

Dinesh · Post by **Dinesh** » Mon Dec 30, 2013 5:46 pm

jsfisher wrote:The World's Worst Holographer

Doesn't that make you the Most Interesting Holographer?

{cf - related, but different - The Interesting Number Theorem (This is a real mathematical theorem!):
Claim: All numbers are interesting.
Proof: If there is a set of uninteresting numbers, then this set must cotain a set of numbers for which there must be a smallest number of the set. But, if there exists the smallest uninteresting number, then this number is interesting for being the smallest uninteresting number.}

jsfisher · Post by **jsfisher** » Tue Dec 31, 2013 1:00 am

The saga continues...

Adhesion on the third variety of acetate was iffy at best. The water development bath took a big toll. I was hoping that I could get an interesting result using a cheap 405nm laser diode. No such luck. Turns out that the acetate sheet with the best adhesion was also the one with the worst transmission of near ultra-violet.

Just to prove a point, I tried 532nm. A guessed at 14 minutes. I got a semi-peeled dim, red result, so that made me happy. (It's red because of the 1-30-300 formula.)

At any rate, I did go back and coat some more sheets. This time with a smooth rod using the tape as a spacer. I must say, the gelatin responded much better to the smooth rod than to the threaded rod I had tried a few nights before. It seemed to lay out a thin, even coat with one even stroke. I have no way to measure, so don't ask about actual thickness. In the previous attempt, the gelatin that pealed off seemed like the thickness of cellophane. This seems thinner.

I used a 5-30-300 formula this time in anticipation of more 532nm tests.

After a day of drying (just like before), the Scotch tape pulled off without taking any gelatin with it (not at all like before). In the previous test, the gelatin appeared soft and thick. This time, thin and hard.

More to follow....

/JSFisher
The World's Worst Holographer

jsfisher · Post by **jsfisher** » Tue Dec 31, 2013 1:06 am

Tony DCG wrote:The World's Worst Holographer could be the most interesrting man in the world

Dinesh wrote:
jsfisher wrote:The World's Worst Holographer
Doesn't that make you the Most Interesting Holographer?

I feel like I should make a Dos XX reference.

(By the way, Dinesh, my degrees are in Mathematics, so, yeah, I know how the least interesting instantly becomes the most interesting.

)

Martin · Post by **Martin** » Tue Dec 31, 2013 8:42 am

jsfisher wrote:Adhesion on the third variety of acetate was iffy at best. The water development bath took a big toll.

Treating the acetate (or triacetate) film with a strong alkali may improve adhesion of the gelatin layer.

I was hoping that I could get an interesting result using a cheap 405nm laser diode. No such luck. Turns out that the acetate sheet with the best adhesion was also the one with the worst transmission of near ultra-violet.

Sounds like that film may already have a surface coating with some fine particles (maybe silica or alike) that have some absorption at 405nm.
Perhaps you could still try to contact copy a transmission grating...