Wood glue/water to seal MDF end"grain" necessary for Duratex?

[aarond]

I'm working on a largerish sub project. It's an old school JBL 1500GTI car audio that would ideally work in a 3 cubic foot vented box but the I've opted for a 7.5-8cf box in an extended bass shelf alignment. Power is Dayton SA240. The ultimate goal is to have a test box for the 18" Dayton HO sub. I'm learning several construction techniques as I go along. Referencing the linked video, how necessary is it to seal the raw edges of MDF when using a heavy coating like Duratex? The PE video says to use a 1:3 wood glue/water mix to seal. I did that on my baffle but the mix seemed pretty watered down and while I think it did something I don't think it did much. After watching the rest of the video again the Duratex seems to be pretty dang thick which makes me wonder how necessary the sealing is with this product.

https://youtu.be/NcydtduDNec

The video should load at the relevant place, if not 8:05 is the spot.

[Steve Lee]

IME you cannot over-seal the exposed end grain of any material - best to do several coats of sealant and sand between coats to build-up a dense/hard surface before applying your finish of anything.

As usual, YMMV - experience can only be had by doing and trying . . .

Good luck, Sir.

[billfitzmaurice]

Duratex is like a Papal Indulgence: It forgives a lot of sins. A single coat of sealer should suffice. If you're using more than one coat of Duratex you may not need to seal at all. I never seal with plywood and with two coats sprayed on you can't even see the grain of the wood.

[Steve Lee]

Listen to Bill ^ Fitz.

[aarond]

Duratex is like a Papal Indulgence: It forgives a lot of sins. A single coat of sealer should suffice. If you're using more than one coat of Duratex you may not need to seal at all. I never seal with plywood and with two coats sprayed on you can't even see the grain of the wood.

Bill, do you sand the sealer at all? It dried to a slightly rough but fine texture. Sanding is no big deal but I don't want to risk sanding through the sealer if sanding isn't necessary.

Also, do you have any experience with PE's ExoHyde product? Seems like it might be the same product but about 25% cheaper for a gallon currently.

[billfitzmaurice]

Unless it's really rough don't sand, the DuraTex texture will hide it and it will adhere better as well. If it's really rough a light sanding won't remove the filler from the pores. I have no experience with ExoHyde. BTW, DuraTex cures best when it's baked in the sun. I do my spraying in my backyard and let the cab sit in the sun for a day. If you don't do that it can take a week or more to fully harden.

[aarond]

Thanks for the tips. It's cold with snow on the ground in KS. I'm not sure how quickly this stuff would cure even on a sunny day. I do have a utility room in my basement that I can set up in. I might do that and play the waiting game. Hopefully the dry winter air speeds things along well enough.