Spincoating emulsion

[wildbillbugman]

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]

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]

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]

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]

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]

Spin Coating 30x40"

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]

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]

Keith;

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

PE

 

[keithwms]

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]

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]

Ooh I'm getting plates too? Goodie!

 

[wildbillbugman]

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]

It's all good. Thanks.

 

[DaveTheWalker]

I realise this is an ancient thread, but does anybody know if this experiment got anywhere?

 

[Nitrous]

I realise this is an ancient thread, but does anybody know if this experiment got anywhere?

i agree, an old but interesting thread.
Any progress?
Doug