how to make wooden glass dome bases airtight?



Just a thought but you might want to consider a lacquer seal instead of silicone.. Glyptal lacquer is used in high vacuum work--very little gets past it. Probably not what you want to use--the color is hideous--but you aren't trying to hold a high vacuum either.
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On 10/02/2017 11:03 PM, J. Clarke wrote:

I'm beginning to think that the problem is in fact that the base inside of the dome wasn't sealed with shellac. I had removed both the domes and the shadow boxes from the living room and placed them in one of the bedrooms and closed the door until I had time to redo them. Today, I decided to redo the domes. One dome came off easily after a cut the silicone around the base; the other dome glass cracked while removing it, luckily I had a spare dome glass. This time, I drilled a 3/4" hole in the bases so I could either discretely add and remove silica gel or moth flakes, etc. There is an "observation area" on the top side, within the dome, but carefully placed (as to not be an eyesore), so that I can see the condition of the silica gel. If it turn pink, I'll just peel off the aluminum tape I sealed over the hole on the bottom side, empty the existing silica and replace with new.
With the domes out of the bedroom where I had them stored, I still had the shadow boxes in the bedroom. When I had to go into the room later in the day, I didn't notice any moth ball odor unlike when I had the domes in there too. Since I completely shellac coated the shadow boxes (all wooden surfaces), I bet it created a good enough seal to keep the moth gases contained. Perhaps the suggestions were correct that I should have completely coated the wood underneath the dome as well, but the problem is that I would have to remove the carefully placed bark and branches to clear the base.
Well, I'm pretty happy now. At least I can check on the moisture content by the silica color and easily change it out if I need to. As long as the seal is tight, pests shouldn't be an issue and mold can be prevented by keeping silica gel active.
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On 10/2/2017 11:39 AM, JBI wrote:

I'd have thought the shellac would do the job but it seems you only did it on the outside. You still have alternatives to consider. I'd try an epoxy coating on the inside.
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On 10/02/2017 03:30 PM, Ed Pawlowski wrote:

The problem here is that I have branches, bark, etc along with the insects already glued to the dome base and all of that would have to be removed first. If I'm going to open it, I'll just have to remove the moth ball bags, but keep the silica gel bags, and reseal. Since the flakes have already been in there for a month anyway, and act as a fumigant, the residue should remain hopefully for long enough until resealed and the silica brings the humidity back down to low levels. The big threat of a preservation like this is mold (from excessive humidity), and pests that eat the insects (if not well sealed in their enclosure).
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Just wanted to update my initial thread. I decided to go with hermetically sealed acrylic canisters (the kind used for airtight food storage). I decided to keep the wooden bases from the original domes because I already had the butterfly environments glued to them (along with the butterflies), so removal of all of that would be prohibitive. The task was then trying to find a suitably sized canister. I couldn't source them locally, but I was able to get ones close to the size I'd need online... all I had to do was carefully sand the perimeter of the wooden bases a bit so they would fit into the canister. To save time, I used my angle grinder as that part of the base would be hidden by the canister band anyway (I am using the canisters inverted for display). The air from the grinder detached two butterflies and I lost antennae on two others, but a little careful repair work and all back to normal. An hour later and the new environment is all set up. With the hermetic seal, I have several moth flakes inside, along with silica gel, and there was even enough room on the underside to add a humidity meter. Two hours later and the humidity has dropped significantly and I don't smell a trace of the moth flakes! And this environment is a lot easier to service if it ever needs it as there's no gluing that needed done!
Now in all fairness to the original bases with glass, I believe that if I had sealed the entire base with shellac, I think this would have worked when used with the silicone sealant. One my two existing unused domes, the plan will be to file down the bases so that they just fit into the dome glass; there will then be a round metal base underneath and the silicone seal will be the glass to the metal base. Someone had suggested a glass base early on and I may do that if I can find the right diameter glass, but I'll just use cut out aluminum flashing in a pinch and no one will see this underneath the original dome base. With the metal to glass seal with silicone, I'm confident moth gasses won't get through, but I'll do my first dome just as a test to be sure.
Well, that's the progress that's been made up to now. Really happy with the acrylic canisters, just don't want to have too many unused glass domes!
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On Tue, 19 Sep 2017 09:40:13 -0400

not sure what mothballs are made of but i think poly coatings are close to inert once they have cured completely
i always thought they vacuum sealed those kind of displays
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On 10/14/2017 10:08 PM, Electric Comet wrote:

The particular moth crystals I'm using are made of paradichlorobenzene which, if breathed for too long, can be damaging to anything living around it. That's why it was essential to have a sealed enough environment to make the out gassing factor negligible. The problem I had was that I was unable to seal the base domes completely as the out gassing issue was discovered only after I had completed the dome environments. I turned here for suggestions and several coats of shellac were suggested. While this appeared to work somewhat, I wasn't able to seal the tops of the wooden bases completely since I already had the environments glued in place and I believe these still unsealed areas was where the moth crystal gases escaped.

I'm not sure how or even if this should be done since the butterflies inside are already fragile to begin with. My solution turned out to be using hermetically sealed acrylic canisters. No out gassing issues or gluing, so the environment inside can easily be changed, updated, or repaired at any future time.
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On Tuesday, October 17, 2017 at 11:23:23 AM UTC-4, JBI wrote:

Hermetically sealed? It's too bad that Ed McMahon passed away. He could have helped.

https://www.youtube.com/watch?v=9m_dT0wsrGI

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On Tue, 17 Oct 2017 11:23:17 -0400

always thought that removing all the air using vacuum was a harmless process
thought that if there is air still inside that would degrade the specimen
so keeping air from getting in is good but also have to remove all the air inside
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