Plywood finishing

A customer asked me to make five boxes for him using 3/8" Baltic birch plywood. I tried to convince him to let me use solid wood, but he wanted the plywood and offered me $100 each for five boxes, size 10"x6"x5". Hard to argue with that! Anyway, I'm wondering what the best finish is to use on these boxes. The corners are box joints, and the top and bottom will simply be glued onto the box frames (again, per customer's request) so the "endgrain" of the plywood will be exposed, if that makes a difference.
Second question: I'm thinking it would be easier to apply finish to the inside surfaces of the box pieces before I glue them together. If I do this, should I cover the areas which I will be applying glue to (like with painter's tape) before I put on the finish? Thought the finish might react with the glue and hinder adhesion.
Thanks for your continuing help!

Glue doesn't adhere well to any finished surface, so covering the glue areas with painters tape is a good idea. Cut your fingers for the box joints slightly long and then sand them flush to get a really smooth end grain, which will finish better. Water based polyurethane or the MinWax Poly-Acrylic finish goes on quickly and dries quickly. It will raise the grain after the first coat so plan on resanding.

I like to apply one coat of Sealcoat Shellac to BB plywood drawers first and then follow up with a WB topcoat. The shellac greatly reduces the grain raising that happens with WB products and gives the wood the look of a solvent based topcoat as well. If you do a good job sanding the end grain BB looks great after it's finished. I would spray the boxes, at least the outsides. If you don't have spray equipment, Sealcoat is easy to wipe or brush on one coat w/o problems, and many WB finishes brush on very easily with a foam brush.

John

What's going in the boxes? I would spray them if possible. At 10x6x5, 2-3 rattle cans of shellac, lacquer, or poly will work. I'm partial to lacquer spraying because it's just so darn hard to mess up.

I do think it's worthwhile to mask and pre-finish the insides with at least one coat of finish - just to make removing the squeeze out from the glue up easy.

Quote:

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Originally Posted by Jerry Lawrence

the top and bottom will simply be glued onto the box frames

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Quote:

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Originally Posted by Jerry Lawrence

Second question: I'm thinking it would be easier to apply finish to the inside surfaces of the box pieces before I glue them together.

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Why would you even worry about the inside finish is it's not going to be visible?

Thanks for the replies and great suggestions!
Darius, perhaps my statements were a little misleading. When I said the box tops and bottoms will be glued onto the frames, I meant as opposed to being rabbetted into the frame so the endgrain wouldn't show. After gluing them on, I'll cut the box frame so it will open. Even though the customer is going to install foam cushioning inside the box to support its specific contents, at $100 per box, I'm still thinking I should at least put on one or two coats of finish.

OK, got it.
If the insides of the box are to be lined with foam then I'd use shellac for the inside finish. Pretty much instant gratification.

For the outside, considering the very porous nature of the edges, I'd spray them with a 1:5 solution of water and Weldbond, and then a coat or two of WB poly.

+1 on the Seal Coat.
Bill

I build high end (I.e. expensive)tack trunks and lockers for the horse show crowd and use Baltic birch for all the interiors and related wood products. (Www.blackberryhollowtacktrunks.com)To finish I sand with 180,wet with water to raise the grain,sand again with 180 then apply 3 spray coats of wb lacquer, sanding with 1000 grit after second coat. Using lacquer allows me to apply a coat every 15 mins -1/2 hour. All wood products in box form have box joints. If using box joints it would be quite easy to mask glue area and finish prior to glue up. But if the inside will be covered anyway why bother finishing. For the interior of my tack boxes I use carpet so finishing is a waste of time and material.

I am in the process of building a shoe rack/cabinet for our under-stairs closet. I've finished two of the boxes, and have one more to go. I am using Appleply for the box and will use 1/2" BB for the shelves, all exposed plywood edges. To highlight the grain, this is the finishing schedule I used:

Sanded all the panels up to 320 grit sandpaper, including the edges. The edges looked almost shiny at this point.
Applied one coat of BLO and let it dry for a week.
Sprayed 3 layers of dewaxed shellac. I had garnet and blonde so mixed them about 1/3 garnet and 2/3 blonde to darken the panels a bit more. Sanded between layers with 320 grit sandpaper.
Followed by 4 layers of General Finishes Polyacrylic Semi-Gloss.

Came out pretty decent. I'll see about taking some pictures.

To ensure I wouldn't roundover the edges, I stuck pieces of plywood on each side of the panel with double-sided tape to support the ROS while sanding the edges.