update on Hxtal testing
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Joe Farina
update on Hxtal testing
As a potential candidate for sealing DCG holograms, the Hxtal epoxy is doing very well in the high-humidity enclosure (~80% RH). After two months, no signs of any change. (The Hxtal was used in combination with the recommended silane.) The other test piece, which was sealed with a UV optical adhesive, isn't doing so well, and all four edges were de-laminated to a depth of 1 to 3mm.
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Dutchelm05
update on Hxtal testing
Interesting Joe,
Would you dare an underwater test?
Best Regards,
Tony
Would you dare an underwater test?
Best Regards,
Tony
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Joe Farina
update on Hxtal testing
I would like to do an underwater test, which would be an "accelerated" test. The only problem is that, like all accelerated tests, it's only an approximation (or in some cases merely a guess) to mimic the stresses that would otherwise take place under milder conditions (for a longer period of time).
Of course, people don't store holograms underwater. But sometimes they do keep them in high humidity conditions. To keep something at 80% RH for any length of time is pretty severe, and I would tend to think that's around the upper limit of what needs to be guarded against. Many, if not most, traditional art materials would begin to show damage under those conditions.
Of course, people don't store holograms underwater. But sometimes they do keep them in high humidity conditions. To keep something at 80% RH for any length of time is pretty severe, and I would tend to think that's around the upper limit of what needs to be guarded against. Many, if not most, traditional art materials would begin to show damage under those conditions.
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JohnFP
update on Hxtal testing
Joe, the best and most severe test in my opinion would be to have the hologram in an strongly changing environment. That is, at 80% for a day or so, then in a desiccator (or similar) for a day, then back to 80%, then back to desiccator ...etc. And vary the temp from cold to warm to cold to warm... etc. (fridge to outside in sun?)
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Martin
update on Hxtal testing
I agree with John that one also has to watch for short term climate changes within the glass-DCG-glass sandwich. For example, a sudden fall in temperature may easily create conditions that lead to water condensation (temperature within the sandwich reaching the dew point).
Though that paper (Bigourdan, Moisture and temperature equilibration: behavior and practical significance in photographic film preservation) deals with photographic materials, it might be equally interesting in the context of DCG: http://www.imagepermanenceinstitute.org ... G97moi.pdf
Though that paper (Bigourdan, Moisture and temperature equilibration: behavior and practical significance in photographic film preservation) deals with photographic materials, it might be equally interesting in the context of DCG: http://www.imagepermanenceinstitute.org ... G97moi.pdf
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Joe Farina
update on Hxtal testing
I agree, John, except that "best" and "most severe" are not necessarily the same thing. I do let those test pieces dry out before checking them, and then I replace them in the humidity enclosure.
Accelerated tests work only to a certain extent. Actual ageing and accelerated ageing are two different things. I try to imagine what the likely (or possible) storage conditions for a hologram might be during its lifetime. This might include high and low humidity, and high and low temperature. For that reason, cycling in the refrigerator would be a good test, as you suggest. But I wouldn't go too far in extrapolating the results from a fridge test (or an underwater test) and then use this to forecast actual ageing. Small differences in conditions can often have large consequences. For example, something that can withstand 80% RH indefinitely may only be able to stand immersion in water for a few days or weeks. Or, something that can withstand gradual changes in temperature (over a long time interval) may not be able to stand the same degree of change if it's more sudden. Etc...
Accelerated tests work only to a certain extent. Actual ageing and accelerated ageing are two different things. I try to imagine what the likely (or possible) storage conditions for a hologram might be during its lifetime. This might include high and low humidity, and high and low temperature. For that reason, cycling in the refrigerator would be a good test, as you suggest. But I wouldn't go too far in extrapolating the results from a fridge test (or an underwater test) and then use this to forecast actual ageing. Small differences in conditions can often have large consequences. For example, something that can withstand 80% RH indefinitely may only be able to stand immersion in water for a few days or weeks. Or, something that can withstand gradual changes in temperature (over a long time interval) may not be able to stand the same degree of change if it's more sudden. Etc...
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Joe Farina
update on Hxtal testing
As of today, the pieces of glass sealed with Hxtal appear to be unchanged, with no signs of delamination. The other pieces, which were sealed with UV optical adhesive, had substantial delamination, and the hologram was beginning to vanish along the top edge and two corners (about 6mm of gelatin had been cleared on all 4 edges of this latter piece, so the vanished areas exceeded this distance).
These two pieces have heen in a ~80% relative humidity environment for 4 months, and had been removed occasionally to dry out, and to check for signs of delamination.
So, things are looking very good for Hxtal with a silane pretreatment.
These two pieces have heen in a ~80% relative humidity environment for 4 months, and had been removed occasionally to dry out, and to check for signs of delamination.
So, things are looking very good for Hxtal with a silane pretreatment.
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Sergio
update on Hxtal testing
Also I think interesting. About the video, the A-1100, amine silane were coated with the help of an alcohol solution? In this case guess the water content must be minimum to avoid hydrolisis before coating so the most alcohol must be used, and the layer would not need a heat air blown to eliminate water vapour traces before applying Hxtal? I guess the high chemical resistance of epoxy forms a good barrier to water vapours (diffusion). Thanks and keep the good working.Joe Farina wrote:As a potential candidate for sealing DCG holograms, the Hxtal epoxy is doing very well in the high-humidity enclosure (~80% RH). After two months, no signs of any change. (The Hxtal was used in combination with the recommended silane.) The other test piece, which was sealed with a UV optical adhesive, isn't doing so well, and all four edges were de-laminated to a depth of 1 to 3mm.
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Joe Farina
update on Hxtal testing
Those are good questions, Sergio. Yes, the silane is in a pure alcohol solution. The supplier of the silane (His Glassworks) stated that even a little water contamination can reduce its effectiveness.Sergio wrote:About the video, the A-1100, amine silane were coated with the help of an alcohol solution? In this case guess the water content must be minimum to avoid hydrolisis before coating so the most alcohol must be used, and the layer would not need a heat air blown to eliminate water vapour traces before applying Hxtal?
On my Hxtal test piece, I just used two pieces of plain glass, because I didn't have a hologram handy. Nonetheless, I can clearly see if the glass delaminates, without having a need for the hologram. So I didn't have to address the question of the silane getting on the gelatin. But I'm not planning on having the silane contacting the gelatin itself, just the edges of the plate which have been scraped clear of gelatin using a razor blade. So, I plan to apply the silane to the entire surface of the blank cover plate, and for the other plate carrying the gelatin, I plan to scrape off about 12mm of the gelatin on all four sides, then apply the silane to about 8mm of this cleared area (using a cotton q-tip) without touching the gelatin. The alcohol in the silane solution evaporates almost instantly.