Casting Resin

This is a forum to share experiences and ideas about holography.
Dutchelm05

Casting Resin

Post by Dutchelm05 »

Dave talked about using a resin for sealing holograms.
I wanted to find a good cheap way to seal DCG holograms that were not the best quality for display but to keep for reference. So I bought some.
I performed two test:
1) Dunk in hot water (180F) for several hours.
This worked well without any sign of the seeping. I also dunked it in cold water to see if the change in temperature would cause shifting. This worked well also. For the heck of it I stuck in an ultrasound cleaner and that also maintain a seal.

2) I left the hologram for two days outside in direct sunlight.
I wanted to see if the resin would yellow or crack. It did not. I also stuck it in a UVO cleaner at work. This is a plasma cleaner but uses a UV source. I saw no signs of yellowing or discoloration.

I think it is cheaper than uv cure epoxy and seems to work well. Not sure if it is a replacement.
If there are any quick easy test anyone can think to try, I can see what happens.

I am still a little broken up over the Jon and Kate break-up but can manage to carry on.
Peace all.
Tony

Thanks Dave for turning me on to this stuff.
Joe Farina

Casting Resin

Post by Joe Farina »

Hey Tony. Sealing DCG holograms can be quite a complicated issue, but I have been looking at the problem for many years, so I feel qualified to talk about it.

If epoxy or UV resin (or probably any similar adhesive like the one you used, which I assume is polyester) is used to sandwich two pieces of glass together, the intial bond may be quite strong. For testing, dunking in water (even for a day or two) is definitely not adequate.

The reason some epoxy bonds fail, for example, is slow, long-term exposure to water vapor in the air, such as in prolonged high ambient humidity conditions (i.e., 75% RH or higher, for many days, but more likely weeks). These kinds of environments definitely do occur. The epoxy in such a sandwich will slowly absorb moisture through its edge. Very gradually, the entire layer will become filled with moisture. This takes considerable time. At some point, and especially if the bond strength is not too high, the mositure in the layer will begin to leave the layer, and migrate to the glass (at the polymer/glass interface). Glass actually has a very strong attraction to water. (All glass exposed to normal humidities will have a layer of water adsorbed to its surface) This strong attraction causes water in the polymer layer to go through the interface, and become chemically adsorbed to the glass. When that happens, the water will often displace the polymer at that point, and the polymer will separate from the glass, thus causing failure. This is especially true in the case of epoxies.

For UV adhesives, other factors may come into play. Stresses can form due to uneven UV curing which can cause failure later (these are detailed on the Summers Optical Adhesives website).

I am currently doing long-term tests in a controlled humidity enclosure that maintains about 80% RH.

If you want to keep DCG holograms stable (and are not producing "finished" holograms for sale, etc.) I would just give them a very thorough drying (say 6 hours in a conventional oven at the maximum allowable temperature, preferably in a vacuum oven since I think you have one available, or maybe just a good microwaving. Then store them in a reasonably low RH enclosure, say something that keeps the RH under 65% or so, but preferably under 60%. I've used a moisture-absorbing material in such an enclosure (for use in boats to keep them dry) and this seems to work. Or maybe silica gel will do the trick also, if you check the RH in the box or enclosure occasionally with a meter. Jeff Blyth once said that by keeping DCG holograms in a very dry condition (in an enclosure with dessicant) for a long period of time (think it was around a week) the resulting hologram would be stable in all normal humidities, and the only way it could be destroyed by moisture was by allowing liquid water to get on it (by condensation for example).
Dutchelm05

Casting Resin

Post by Dutchelm05 »

Thanks Joe, very interesting stuff.
Joe Farina wrote:which I assume is polyester
yes it is

I wonder too if the edge of the emulsion is a factor? If I razor off 1 inch vs 1/4 inch if the barrier is sigificant?
Can you coat the edges? I've done this with epoxy with the thought that if moisture cannot get inside the two pieces, then it has a better chance.

So what if I dunk it in 100% water for a week? would that be an accelated test? just enough to get a warm fuzzy
Joe Farina wrote:I've used a moisture-absorbing material in such an enclosure (for use in boats to keep them dry)
what material is this Joe? Can you link me to something that discribes it?
Joe Farina

Casting Resin

Post by Joe Farina »

It's called DampRid and is available at marine supply stores, at least around here. Whatever container you use, I would elevate the holograms off the bottom as much as possible, since it seems that moisture goes to low areas. I would also put a cheap humidity meter inside, and check it about once a week (until you see how the DampRid behaves, then you might be able to leave it alone for a longer time period). As long as the holograms are good and dry in the first place, I think you could probably keep them indefinitely in this manner.

Everything else being equal, it's probably better to razor blade as much gelatin away from the edges as you can, since failure first occurs at the edges, and gradually works its way inward. A quarter inch should be good in most cases (that is, if you have confidence in your sealing method). But the more space, the better, and a full inch would definitely provide extra protection.

The week-long test under water would be good. The only problem is that typical damage to DCG is done by long-term expsoure to RH around 80%. It's not necessarily a good correlation to accelerate the test by putting it under water. But it is more severe, and will certainly cause failure sooner, so it might be worth a try.
Dutchelm05

Casting Resin

Post by Dutchelm05 »

Thanks Joe,
Really great to hear from you as always.
I will dunk this one and let you know. It has less than 1/4 of gel razored off so it should be more extreme.
Like I said I have a lot of holograms that just don't make the grade but have interesting qualities or is good as a reference. My lab is full of dead soilders.... :doh:

Around here atleast 80% RH is rarely seen. The few worthy DCG holograms I have are indoors and in a box. Hopefully the grandkids can enjoy them one day.
Joe Farina

Casting Resin

Post by Joe Farina »

Tony, regarding your planned test, there is something else I wanted to mention. To get a clear picture of what's happening, I would be sure to let your hologram "dry out" after removing it from the water. Probably 1 or 2 days would be sufficient, to dry out those areas of the polymer that are a few millimeters deep. It would probably take a lot longer to dry the layer throughout. But any damage that occurs will probably be done in the first few millimeters, or maybe in the first 1/8 to 1/4 inch, after soaking in water for a week. After you pull the hologram out of the water, there may be a series of "micro-bubbles" along the edges (or some other type of effect), but they may not be visible because they are filled with water at that time. So that's why it needs to be dried somewhat, so that the water is removed in those areas (so you can see the bubbles or whatever else appears). Those areas will probably be cleared of gelatin (if you razor blade them) so the hologram might be fully intact (so you might not be able to judge the results of the test by looking at the hologram, if the soaking occurs for a week only).

Regarding the likelyhood of high humidity for any length of time (80% and above for a week or more), I agree it's not a common occurrence in normal indoor conditions. The problem arises when DCG holograms go into storage. If they are stored in a basement, or an unheated garage, then real problems can occur quite quickly. I have seen this effect over and over again. Part of the problem is that people often view them as "glass" or as "sealed in glass" and have a false sense of security about their durability. The glass simply serves as a barrier for any "gross" variations in humidity (short term), or as a barrier to liquid water. I have a beautiful hologram by August Muth that I stored in an unheated building, and the seal began to fail quite quickly, because the humidity became high and stayed that way for a long time.

I am currently testing an archival epoxy used in glass conservation, which is called Hxtal. It's also used by glass artists, and has a fairly long track record. In my current test, and after about 2 weeks at 80% RH, it's doing very well, with no signs of damage yet. I have my fingers crossed. With Hxtal, it's important to use the silane pre-treatment (called A-1100 Amino Silane, or gamma-aminopropyltriethoxysilane). This is the same stuff I sent you earlier. The Hxtal is avilable from His Glassworks. I also made sure to de-gas the epoxy after mixing, to get rid of the air that's introduced when mixing the two components (A and B). For the vacuum system, I used two refrigerator compressors hooked up in series, which can get a vacuum of 29.5 inches. The degassing and application of Hxtal is also shown in the video on youtube which I linked to earlier.
Dutchelm05

Casting Resin

Post by Dutchelm05 »

Thanks Joe,

I have more comments but had a quick one if I could.

Many of my unsealed holograms that I am just too lazy to seal but don't have the heart to toss are in simple zip lock bags. Is the enough to protect them? I have many that are several years old (even some unseal and no zip lock bag) with not problems.

Thanks,
Tony
Joe Farina

Casting Resin

Post by Joe Farina »

Hey Tony. If they lasted several years, then I would say there's a good chance they will continue to last, unless there's some unusual change in the RH. The drying of the DCG after processing has a big effect on their sensitivity to RH. I gave one of mine a good microwaving, and stored it in my damp basement, and it lasted for a full year before vanishing. The drier you can get them after processing, the more resistant they will be to RH later on. If they can be gotten really, really dry (like Jeff Blyth said) they appear to be insensitive to RH. I guess the only reason they would need to be sealed is to protect them from condensation (which is a definite problem, for example, if you took a cold hologram and brought it into a warm room) and to protect them from mechanical abrasion.
Dutchelm05

Casting Resin

Post by Dutchelm05 »

Two days underwater and all is well.
Monday I will take it out and allow it to dry.
Then back to the water boarding tank.

I will make this hologram talk :twisted:
Colin Kaminski

Casting Resin

Post by Colin Kaminski »

Joe, is it OK if I condense all of this into a wiki post? It is the best information I have found on sealing DCG.
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