update on Hxtal testing

[JohnFP]

Joe, nice o-ring technique., but why not tcuch the gelatine?

[Joe Farina]

It's only the silane pre-treatment that I'm planning to apply to the edges of the plate carrying the gelatin. The Hxtal epoxy would be applied all over. (I just don't want the alcohol from the silane solution to get on the gelatin before sealing with epoxy.)

[Sergio]

Another option using a hard resin is vinyl ester cured with catalysts:

http://www.derakane.com/derakaneControl ... ode=536001

the Epoxy Vinyl Ester Resin is very strong, I guess although the styrene may be a nuisance.

[Joe Farina]

As my final installment on this Hxtal testing thread, I took a few photos of the results. The small hologram on the left was sealed with UV adhesive, and the glass plates on the right were sealed with Hxtal. (The Hxtal test was of two pieces of glass cemented together, without a hologram, because I didn't have one available. Any problems due to humidity could easily be identified, though, by visual inspection.) Both were placed in a ~80% relative-humidity enclosure for about 7 months.

The UV-sealed piece slowly and steadily showed signs of moisture infiltration. It did better than I thought, as I was expecting it to have completely vanished long ago. The Hxtal piece showed no change whatsoever. It's difficult to tell from the photos, but it has no signs of damage.

So my conclusion is that Hxtal is very effective, by far the best optical adhesive that I've ever used. But I think it's important to use the silane pre-treatment as previously noted (and as shown in the video). The only caveat at this point is that I haven't used it yet with a DCG hologram, so I don't know how much the Hxtal will penetrate into the voids. Not that this is necessarily a problem, because even with the low-viscosity UV cement that I used previously (that temporarily caused the hologram to dim), the holograms regained their brightness after the cement cured. But I think that Hxtal has moderate viscosity in comparison, and even if the viscosity creates a problem (and I think it's very unlikely that it will) it could probably be easily corrected by letting the Hxtal "set up" a little bit before application, to increase the viscosity.

So, in conclusion, a very enthusiastic "thumbs up" for Hxtal.

[Colin Kaminski]

Thank you Joe for sharing the results of so much effort.