Quote:
Originally Posted by JB5pro
would have been a liquid poured in between the glass and CRT, covering the entire viewing surface, forming to a crystal-clear, rubber-like sheet about 1/8" thick.
I had removed the glass by lightly heating the center area with a hair dryer. The outer areas were seperated because the material was rotted by some white mold-like substance. Thanks for thinking about it.
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I would have recommended RTV-615, but the price has gone through the roof. Sylgard 184 would work, but will still cost about $100 assuming no mistakes. I've not used Sylgard 527. but it sounds like it would work and be less expensive. It would be a very soft layer.
The problem is that 1/8" over 10" diameter is 644 ml of material. The Sylgard 184 0.5kg kit would provide about 485 ml since it has a density of 1.03 You'd want at least 20% more than 644 ml to work with. So, you'd need to buy two kits.
The 527 is much less expensive, but less rigid. Over such an area I don't know that it would be an issue.
After mixing either of them you would need to vacuum degas them to get the bubbles out. Silicones are pretty permeable to oxygen and if you don't degas it some of the oxygen may form bubbles when it cures even though you didn't see any to start with. On the other hand, often small bubbles will dissappear during the cure if you degassed it to begin with. They just get disolved into the silicone.
You would have the safety glass face down on a soft surface that keeps it from rocking. If it wouldn't be distracting, the easiest thing would be to superglue three 1/8" thick disks around the outer edge to act as spacers. Pour the silicone into the center without entrapping bubbles. Then slowly lower the CRT touching the center first in only one spot. Being care to not wiggle about continue lowering it letting the contact spread slowly outward displacing the air. Done carefully, there will be no bubbles. It's important to have only one contact spot to start with.
The cure of these materials is inhibited by contaminates. Vinyl tape, anything with plasticizers, oils etc. will cause them to not cure.
Acrylic resins would be less expensive but are quite hard and shrink a lot during the cure, which might damage the CRT.
They probably used some heat curing or melting polymer that would be difficult to work with, without the proper equipment.
It's important to try a small sample of the encapsulant to see how it cures and applies.
It cures slowly so you have time to take things apart if it doesn't look good and you only lose the cost of the silicone. It's a bit difficult to clean up in such a case. The safest solvent would be 200 proof ethanol or denatured ethanol.
No guarantees.
There are special primers to increase the adhesion to glass. I wouldn't recommend it because you might need to take it apart later.
Oh, and when you pump on it to degas it, it's like soap. It really foams up before collapsing into a clear pool. You need a large container to start with or else be extremely patient. The latter is probably required. It might work without degassing, but for my applications I can't risk that.
http://www.ellsworth.com/display/pro...63&Tab=Vendors
http://www.ellsworth.com/display/pro...16&Tab=Vendors
And after reading the thread in this forum I'll see what I can find out about PVA. John