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keithwms
01-11-2012, 02:44 PM
My shipping address is Keith Williams, UVA Physics, 382 McCormick Road, Charlottesville VA 22904. Sample size... well I can do very small samples if desired. I was planning to use ordinary microscope coverslips cut into ~1x1" squares. 1mL would easily coat that, many times over.

Question is whether you want me to test exposure, or you... I could do simple tests.

Wish I had some blank plates for my rb, it has plate holders for that, let me see what I can come up with....

The big advantage of spin coating is that it is extremely economical in material. Whatever your emulsion costs, I can tell you that some of the resist I use are far more costly. And unused material can actually be recovered... partially at least.

I suppose now would be a good time to mention that I am also looking into adapting an inkjet for paper coating...

Photo Engineer
01-11-2012, 02:47 PM
Keith;

I would like to remind you that the dry layer should be about 10 - 100 microns depending on emulsion which means that the emulsion itself must be put down at about 5 - 7 mils thickness. Can you do that? Resists are put down much thinner.

PE

keithwms
01-11-2012, 03:32 PM
I can't promise Ron, but I can certainly try, and in the worst case, multilayer spinning is not difficult.

Regarding typical thicknesses, I wonder if that's really a necessity or if that's just what the bulk coaters can do best....

wildbillbugman
01-11-2012, 04:32 PM
Keif,
My newwest batch is 0.25 M, based on the MW of AgNO3. Would 100 grams be enough to do all the tesing you would like to do?.
I will supply it in a light-proof container. Refridgeration is not required.. It is a blue sensitive emulsion in its current form. My "standard" developer is undiluted Kodak D19 for 8.5 minutes..
I do not have any glass plates that would fit your coating machine, as my usual plate size is 5"X7". Maybe someone who is sending you a sample could send you some 4"X5" plates. I think that your amber safe lights should suffice for this emulsion.
I am quite excited about this emulsion because, even with extended soaks in developer, it shows no signe of fogging.
I will get this off to you tomorow, Thurday.
Many thanks for your intrest and desire to help,
Bill

keithwms
01-11-2012, 04:39 PM
Cool Bill, I look forward to seeing whether it works. Yes, 100 gr is probably, what, 25-50mL? Should be plenty. I can get some plates, no worries.

wildbillbugman
01-11-2012, 04:39 PM
Regarding minimum thickness, I think that this might be , in part, developer dependant. With my emulsions, D19 yields deep black highlight areas. Pyro on the other hand yielss week browns.

keithwms
01-11-2012, 04:42 PM
Yep I guess the thing to do is a wedge-like test and just see what provides optimal contrast. But first things first, let's get some on some glass!

Photo Engineer
01-11-2012, 05:32 PM
Keith;

The thickness is based on concentration and being able to get Dmax. If you coat too little you can't get Dmax. And, this is based on how much one can actually make the emulsion capable to do this.

PE

Hologram
01-12-2012, 01:28 AM
Keith;

I would like to remind you that the dry layer should be about 10 - 100 microns depending on emulsion which means that the emulsion itself must be put down at about 5 - 7 mils thickness. Can you do that? Resists are put down much thinner.

PE

I guess coating speed for gelatin AgX emulsions needs to be pretty low.

In the context of holography spin coating has been widely used - both for preparing photoresist layers for embossing and the making of holographic optical elements (HOE) mainly. Richard Rallison, one of the pioneers of DCG, put a couple of papers online that explicitly dealt with spin coating. After this passing they are no longer available.

In his paper, Control of DCG and non silver holographic materials (SPIE 1600, 1992), he wrote:

A variable speed turntable capable of 50 to 100 RPM will coat films of gelatin or PVK from 4 to 50 microns on 8 x 10 inch glass or plastic substrates. Plates as small as 3 inch diameter or as large as 16 x16 inches have also been successfully coated with this range and technique. The turntable should be equipped with a surface or arms that will mate to a removable tray that is one or two inches larger than the substrates being coated. We have used ordinary variable speed phonograph players with pie tins turned upside down and glued to the turntables and we have used Dayton variable speed gear motors with heavy duty arms attaches. Both devices worked very well.

Trays have been made up of stainless steel, plexiglass, polyethylene dishpans or modified from aluminum cake and pizza pans. The best trays have straight sides measuring 2 1/2 to 4 inches high and are fitted with 3 rubber posts inside and outside. The posts inside hold the substrate an inch or so off the bottom of the tray and the outside posts serve to level the tray during pouring of solutions and to center the tray during spinning. The spinning tray and substrate may generate useful turbulence that aids in drying and distributing the solution. Excess solution is caught in the tray and emptied between substrates then is easily soaked clean in hot water after a days activities.

An important component that augments drying and uniformity is the blower-heater. It hangs off center and above the whirling tray. Turbulence and heat combine to make uniform coatings in about five minutes. We recommend the use of a variable temperature 600 watt blower such as might be found in the ceilings of some bathrooms. A little experimenting with angle and position will quickly determine the best place to hang this unit in your clean hood or bench area. Coat and examine uniformity by looking for local fringe patterns under a fluorescent lamp or better yet a fluorescent long wave black light.

keithwms
01-12-2012, 08:11 AM
I do have a hair blower :)

I can do low speeds, of course. I suspect that the best result will be for a combination. Maybe one cycle high speed to get an initial wetting layer, and then slow, and then a little bake to even things out.

dyetransfer
01-12-2012, 12:28 PM
I think it should be tried. I'm not aware of this method ever having been used due to the one off nature of the product.

I think it is an interesting idea. Maybe I could whip up some emulsion and send you a jar.

PE

I've heard from John Preston that he used to spin coat very large sheets (perhaps vacuumed down acetate?). The sheets were about 30x40". They were coated with a silver halide gelatin photo emulsion and used for map making somehow. He says they got good even coatings, so I guess it can be done even on a very large scale.
My guess is that this technique is best for very thin coatings, and figured it probably wouldn't work for very thick matrix film coatings.

Regards - Jim Browning

keithwms
01-12-2012, 01:47 PM
I've heard from John Preston that he used to spin coat very large sheets (perhaps vacuumed down acetate?). The sheets were about 30x40". They were coated with a silver halide gelatin photo emulsion and used for map making somehow. He says they got good even coatings, so I guess it can be done even on a very large scale.
My guess is that this technique is best for very thin coatings, and figured it probably wouldn't work for very thick matrix film coatings.

Regards - Jim Browning

Again, it is no big deal to multicoat. And if there were reason to get fancy: some of these coaters have multiple injectors, are fully programmable, so you can push a button and go away. It'd be no big deal to have a plate wetted, spun, aired, baked, wetted, spun etc. ad nauseum. The nice thing about the process is that it is quite scalable, I'd see no problem getting up to full plate size at low speed (couple hundred rpm).

But the proof is, of course, in the pudding. So let's just see!

Photo Engineer
01-12-2012, 01:54 PM
Keith;

Do you want some 4x5 sheets of film or 4x5 plates with the emulsion?

PE

keithwms
01-12-2012, 01:58 PM
Plates. Or do you have other ideas...? I wasn't thinking of dealing with film at all. I mean, I could think about that if there is interest but glass plates would be much, much easier. Film would have to be adhered to a plate and then lifted... could be a pain.

For film I think my idea of adapting an inkjet printer is probably more reasonable.

Photo Engineer
01-12-2012, 02:38 PM
Ok, when I can get away to the PO or UPS I will send you 1 or 2 emulsions and a few plates (4x5).

PE

keithwms
01-12-2012, 04:52 PM
Ooh I'm getting plates too? Goodie!

wildbillbugman
01-17-2012, 05:38 PM
Kieth,
I have promissed you a sample of a non-gelatin emulsion last week. Well I used it all up in testing. I have begun a new batch and will send you some befor I do anythingelse with it.
That will be in a day or two.
Bill

keithwms
01-17-2012, 10:35 PM
It's all good. Thanks.