Temperature

Holography related topics.
alan.bogana
Posts: 19
Joined: Sat Mar 28, 2015 4:03 am

Temperature

Post by alan.bogana »

Hi all,

These days I've been developing some holograms in a room with 24-25 °C and processing them in a chemical bath at 20 °C degrees, with some good results.
I was wondering though how this difference of temperature impact the creation of the hologram. Is it recommended-crucial that both room and bath be the same, around 20 °C (+/- 3 °C) ? Room temperature at 27° C and bath at 20° C is also ok ?? (In my area is going to be quite hot during the next days)

Best
Alan
BobH
Posts: 440
Joined: Tue Jan 06, 2015 10:26 pm
Location: Mesa, AZ

Re: Temperature

Post by BobH »

Developers will work faster with increasing temperature, and maybe the bleaching will go faster too. I'd adjust the time in each according to what gives you best results. Cold washes are best for minimum shrinkage.
alan.bogana
Posts: 19
Joined: Sat Mar 28, 2015 4:03 am

Re: Temperature

Post by alan.bogana »

Thank you ! I'll continue testing.
So the fact of having the emulsion at 25 C (in the room) and then putting it in the 20 C processing bath shouldn't affect the hologram right ? (beside the fact that overtime the bath will slowly increase of temperature, and therefore accelerate the processing).
Din
Posts: 402
Joined: Thu Mar 12, 2015 4:47 pm

Re: Temperature

Post by Din »

It's the temperature at which the film/plate is actually immersed that most affects processing, not the room temperature (within reason). The room temperature/humidity may affect the substrate and/or the emulsion if it's extreme, but to reasonable limits, the room temperature simply warms the surface, the heat penetrating into the emulsions will have very little effect (again, unless it's extreme, ie ~40C with > 60% RH). However, the processing system is actually a chemical reaction that occurs while the film is in the various solutions. Like any chemical reaction, the speed of the reaction is temperature dependant. In other words, the warmer the various liquids, the faster is the the chemical reaction and the faster is the process. This may induce a "slow" film to process a bit better (and various holographers have warmed the developer when the exposure was lower than necessary), but a properly exposed film that's developed too fast will overdevelop.

Imagine I have a set of walls made of some rigid substance protruding just slightly above a bed of sand. As I now pour sand over this, the sand in the gaps between the walls will be lower than the sand on the walls. As I continue to pour sand, the undulations of the sand will eventually even out and you'll have no structure - the whole bed of sand, walls and all, will be of uniform height. The hologram performs best when the level of the sand above the walls is slightly higher than the sand between the walls. As the level of the sand evens out, the hologram gets poorer and poorer, eventually disappearing altogether. The development process is akin to pouring sand into this structure. Developing in too warm a bath is like blasting sand at this structure - you have no fine control.
lobaz
Posts: 280
Joined: Mon Jan 12, 2015 6:08 am
Location: Pilsen, Czech Republic

Re: Temperature

Post by lobaz »

On the other hand, many holographers claim that processing soft Slavich emulsions such as PFG-03M works best at low temperature.
Ed Wesly
Posts: 513
Joined: Wed Jan 07, 2015 2:16 pm

Re: Temperature

Post by Ed Wesly »

Temperature plays an important role in photographic development. Instructions for black and white photographic film would include a chart that prescribes the development for a range of temperatures, typically from 20C to 24C (68F to 75F), or room temperature. Developers are relatively inactive below that range, and bad things can happen at higher temperatures, like emulsions lifting off, but also the reaction gets out of hand. Manufacturers of B & W printing papers usually give a suggested development time at 20C.

Holographic plates are more like photographic printing papers than film. Agfa never gave time versus temperature tables for Holotest films and plates, just 2 minutes @ 20C. http://edweslystudio.com/Formulae/Devel ... ochure.PDF I have often heard that Lon Moore would develop his masters of flowers on Agfa plates at 90F (32C) to cut down exposure times, but there could be the risk of fog, meaning development of unexposed grains, which translates into noise, the bluish-white haze in the image that never gives a good black.

The key to success is keeping the process consistent. If you decide on 20C, or any other ambient room temperature which is easy to maintain, do so. You may want to make some exposure tests and develop them for different lengths of time, but you will find that the longer times, although needing less exposure for decent brightness, bring up the noise.

I have found that the Sphere-S GEO-3 performs better at 65F (18C) maybe because the gelatin is softer, and I learned that trick from TJ (may he rest in peace) from his work with PFG-03M, but not -03C, but all these are in a similar category.http://edweslystudio.com/HnEPortfolio/ColdJD4.html Geola recommends a formaldehyde based pre-hardener for these materials before development at room temperature, but that extra step may not be to your liking.

Find what is comfortable for you to use, both time and temperature wise, and stick to it, because you will hear a variety of opinions here. There is an optimum density for all holographic materials, and how you get there is a combination of exposure time, and development time combined with temperature.
"We're the flowers in the dustbin" Sex Pistols
Din
Posts: 402
Joined: Thu Mar 12, 2015 4:47 pm

Re: Temperature

Post by Din »

lobaz wrote:On the other hand, many holographers claim that processing soft Slavich emulsions such as PFG-03M works best at low temperature.
Sure. The rate of reaction depends on the softness of the emulsion, since this would determine the amount of penetration of the solutions into the gelatin matrix. A soft emulsion would allow greater penetration into the matrix, hence, for the same dev time, the softer film would develop more. It would also depend on such factors as the size of the grain, since the reaction is mostly dependant on the surface area of the grain, which increase as r squared, while the volume goes up as r cubed; this is film dependant. Another factor is the density of halide molecules, which is also film dependant. Of course, the age of the developer is also a factor, especially if you're using a two-part developer.

As a general rule, the greater the temperature, the faster the reaction and so, the rate of development, bearing in mind the above restrictions. But, if the developer is too warm, then fringe braodening occurs and you get non-linearities and also spurious scattering due to grain growth and the development of weak low-frequency gratings that are usually suppressed. However, "too warm" is a little vague. Generally, I'd expect around 20C to be a good starting point, and varying from there dependant on film type and exposure.

There are also the physical developers for very fine grain film. But, that's a different story.
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