how to make wooden glass dome bases airtight?

[JBI]

I have a small glass dome with a wooden base identical to the one shown here:

I do entomology as a hobby and placed several butterflies in the dome over the Summer and then sealed the base to the glass with silicone so that small bugs could not enter and eat the specimens. I also hid some moth flakes inside the dome to ward off these pests just in case they broke through the seal. I didn't think I would have any issues afterwards, but I am having one--- I can smell the moth balls outside the dome, which means the wood is allowing the ball gases to escape. This isn't good as it's a hazard to breathe moth ball gasses. For now, I've moved the dome to an unoccupied area of the house until I find a solution. Is it possible to coat the wooden base, up to the point where it meets the silicone, with something to seal the wood and make it airtight and, if so, what would it be? In a pinch, I was thinking of melting wax and then "painting" it on the base, but not sure this would work or even be effective.

Thanks in advance for any help.

[Sonny]

Also consider, it may not be the wood that's the problem. Your silicone s eal may have been compromised, allowing fumes to escape. If your dome uni t was purchased, I would think the wood aspect has been sealed, hence givin g credence to the silicone seal breakage.

Otherwise, seal the wood with pretty much any poly, lacquer or shellac. Li ghtly sand the wood before applying the finish. I would use shellac (Seal coat, available at most any hardware/paint outlet).

Sonny

[JBI]

Thanks, Sonny. Went with shellac. Just applied it a while ago after sanding. Waiting for final coat to dry (I used two coats). I can already notice a decrease in mothball smell.

One additional question if you don't mind. I have two small shadowboxes, one made from barnyard wood and the other walnut. They are seen here:

Although I'm confident I sealed the rear side correctly since I used a metal backing, I'm wondering how to seal the wooden frames. Could I paint the frames with shellac? Thanks again!

[JBI]

Thanks, Sonny. Went with shellac. Just applied it a while ago after sanding. Waiting for final coat to dry (I used two coats). I can already notice a decrease in mothball smell.

One additional question if you don't mind. I have two small shadowboxes, one made from barnyard wood and the other walnut. They are seen here:

Although I'm confident I sealed the rear side correctly since I used a metal backing, I'm wondering how to seal the wooden frames. Could I paint the frames with shellac? Thanks again!

[Sonny]

Yes. Watch for drips if you brush it on. Sealcoat comes in aerosol/spray cans, also.... may be easier to spray projects as these.

Optional: The barnwood box, my preference.... I like the weathered-wood look, for som e things. Consider leaving it raw wood, no sealing. You can always seal it later. Similar examples: Vertical planter boxes I made for the local Master Gardeners' fund raiser. Scroll right for more pics -

Sonny

[Dr. Deb]

Shellac does a wonderful job of sealing, as you are discovering. The other option for your glass domes (assuming you do not want to open them) is to put a thin coat of epoxy on the rim of the dome and seat it in place.

[Scott Lurndal]

That's not walnut. It's MDF. Yet another reason not to patronize hobby looby.

[JBI]

Thanks. They probably will have to be opened from time to time if for no other reason than to check on the silica gel and moth flakes that are inside. I had to open one once already and simply cutting through the silicone with a sharp knife did the trick. If I was never going to reopen them, I would have definitely gone with the epoxy option as you suggest.

[JBI]

The sealing of the shadow boxes went well. I didn't mention it earlier, but the two aforementioned ones I already had with insects inside plus the same moth flake/ silica treatment and they were sure smelling.

I am now left with three unused domes that have either bare wood bases or in one case, stained. I am thinking of going ahead and applying shellac to the bases now so that they're ready to go for future sealing, but I'm wondering if I should not apply shellac over the area where the dome would be coupled to the base with the silicone? In other words, if I paint the entire base with the shellac, and not avoid the sealing area, would the silicone still form a seal with the shellac coated wood?

[Ed Pawlowski]

Curious, would it be beneficial to give the dome a shot of co2 to get most of the oxygen out?

[Sonny]

Yes. The silicone would form a sufficient enough seal with 'most any finish you apply. Even with your periodic breaking of the seal, the/any finish would likely remain intact for resealing, without having to refinish the base.

Sonny

[Sonny]

Come to think of it, for years, it's been common to see luna moths in Augus t... they come out at night for about a two week period, often unexpectedly flying in front of your vehicle, while driving, certainly catches one's at tention. They're almost as large as your hand. Since childhood, it's be en kinna neat catching and observing one or two, then release it. And the se days, catch & show the younger folks, giving them this experience.

I don't recall seeing any this year. I hope there hasn't been any pesticid e use, or such, to have diminished their population.

&biw=1920&bih=950

Sonny

[JBI]

That's not standard practice with insects, unfortunately. Also, the idea is to keep the humidity as low as possible within the enclosure, to keep mold from forming on the specimens, hence the need for silica gel (as well as thoroughly drying the specimens before putting them in the dome), and to seal to keep other bugs from entering, such as book lice, that might eat the wanted insects. For extra insurance, some collectors add a fumigant or repellent like I have, such as moth balls or flakes. Since this was my first dome, I hadn't anticipated that the moth ball gases would penetrate the wood base, but they did requiring the shellac seal. If I didn't have concern about breathing the gases 24/7, I wouldn't have needed the seal, but I didn't want to be getting a smell of the stuff all of the time.

[JBI]

I hope to come across one. The last one was one my father brought home when I was a teen, about 30 years ago. He was a truck driver in the summer and hauled tomatoes/ beans out of the fields during the summer. He'd end up bringing home all sorts of critters from the lunas to snakes and garden spiders. Unfortunately, I didn't know much about drying and framing in those days, so I must have discarded it. They only live a week once they emerge from their cocoon, don't eat, and simply spend their living time to mate. Next summer, I am considering building a moth trap that uses a mercury lamp in the center to attract them. Either that, or just order a cocoon and let it come out of that. I have a butterfly trap that I set up towards the end of summer this season and it brought in some fairly sizeable moths also during overnight hours.

By the way, thanks for your followup on the shellac. I'm in the process of sanding and coating the unused bases now.

[Leon]

Thoughts after all the ideas.

Some silicone off gasses are pretty nasty smelling as thy cure. IMHO it might not be a stretch to think that those gasses are inside the dome too. do you think that would have an adverse effect on the eminences?

Maybe you need an air tight gasket.

[Leon]

Specimens?

[John Grossbohlin]

Perhaps having plate glass disks cut that loosely fit the inside diameter of the domes would work... Silicone "glue" them to the domes and place the domes on the wooden base to press the disk into final position.

[JBI]

I just wanted to update since I sealed all dome bases with the shellac. Once I had fans no longer running (to either help dry the dome bases or for other reasons), within a short time, I could start smelling the moth balls. I didn't think it was too bad until I was out of the house for much of the past weekend. When I arrived home, upon opening the door and entering the house, the smell was overwhelming.

I am disappointed. I carefully coated all bases with at least two coats of shellac. My guess is that the mothball gases still somehow penetrate the silicone seal of glass dome to wooden base, or because I couldn't seal with shellac any wood under the glass dome, perhaps the gas gets through there too, but originally I thought the outer sealing would stop it. I guess I only have two choices: 1) cut silicone seals to be able to open the domes and remove the moth ball bags, then reseal without moth balls, or, 2) place the complete dome as it is now in a larger, sealable container. My local Walmart has some large acrylic jars with a lockable seal. Problem is that, for the size I'd need, they're expensive. I'm probably going to go with the first option above.

Thanks again for all those who tried to help. I guess it's just not going to work out this way.

[DerbyDad03]

Aren't there any forums for folks like yourself, i.e. hobbyist entomologists?

Perhaps the problem isn't the wood, maybe it's the mothballs. Have you checked with other groups as far as what they do to accomplish their display/preservation needs?

[Ed Pawlowski]

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.