Woodworking peoples, I could use your guidance on making things watertight

I have an idea for a simple project. I want to make a tool for turkish paper marbling. It’ll be a large shallow tray about 15"x21" and it needs to hold 4-ish gallons of thickened water. I’m not an expert in joinery, but I feel confident in my ability to nail a few planed 2x4s together and slap a hardboard bottom on it. What I’m NOT confident in is my ability to join them in such a way that it doesn’t leak all over the place when I go to fill it up.
What would YOU do here? How would you protect such a construction from leaking liquid all over the place? Do you coat the wood in many layers of polyurythane? Do you put something rubber-ish between the boards before joining them? Both? How would you approach this?

@got_tools keeps liquid inside boxes.

You can build that and it would be fun, but for something quick :

Plastic bin

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Well sure I could do that, but I wouldn’t be me if I didn’t make things at least a LITTLE more difficult than they need to be
And besides, every time I branch off in a new direction is a chance to learn how to do something new :+1:

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Lol… if you don’t want to go the easy route of using a pre-made bin and you’re adamant about building something, I would probably think about pool liner in the box you mentioned.

That said…. you’re talking about using hardboard as a base… I’d suggest looking at plywood. Hardboard and water do not mix well in structural environments. Hardboard and weight don’t mix well either.

I agree though that a plastic bin is a more “logical” choice for this application. But logic and DIY for the sake of DIY don’t always mix. (Not that that’s a bad thing.)

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Table or Bartop resin could also provide a good thick plastic coating on the interior. That’s what I use when I make wood goblets or shot glasses. Its not cheap however.

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Ah, I would not have called hardboard not being sturdy enough. That’s good to know, thank you

It’s expensive, but it’s not THAT bad for my purposes. I don’t have a whole tabletop’s worth of space to cover. It looks like there are $20 16oz packs that might be enough for me.

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Maybe an acrylic box? The one here may not be water-tight but it is clearly citrus-fruit-tight:

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At the very least, it would help keep my limes under control
I am wary of acrylic. I’ve probably been doing it wrong, but acrylic boxes always seem to crack at the worst times

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Hardboard disintegrates into dust when wet. And while the inside of your bin might be coated, think about when you toss the water out, if a little gets on the bottom, it will quickly fail.

Plywood will stand up to more exposure, but it’s not a perfect choice either. It too will peel and separate after long term exposure. It will sustain temporary splashes though.

If you’re looking to learn some skills as a purpose of this project, you could consider sheet metal as an option. Cut out a form, Bend the box into shape, weld the seams. Or rivet the seams and then silicon the seams. Either way, learning some basic sheet metal forming is another skill class you could unlock with this project.

This bin gave me the idea that this might be a relatively easy project if I can get the liquid aspect under control. Seems simple enough, but there are probably things I have not considered.

Acrylic Paper Marbling 1 - YouTube

Oooh. Sheet metal would definitely work. I haven’t worked much with metal before, but I know where to learn :wink:

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1- cool video.

2- that looks like 2x4s on a 1/2 sheet of ply. If you made this and then coated the whole thing in a thin layer of epoxy, you’d probably be fine. You could also do many many coats of poly.

3- their drying board looks to be the pressed side of hardboard coated in a poly.

4- their swirl sticks look like 2x4s that are painted in a heavy latex paint layer. That’s another option for water resistance for the box. Not sure how long that would last for a water retaining device though.

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Or yet another skill tree you could consider: making the box and then fiberglassing it.

I don’t think I know what that means, but I’m intrigued

Basically fiberglass cloth and epoxy - not cheap but very waterproof. Boats that go across oceans use this technique. It’s very sandable and paintable (not sure how food safe the paint might be).

I successfully used West Systems Epoxy to seal the metal buckets in the Metal shop/Blacksmithing which were leaking.

For your project, I’d use solid wood (not engineered MDF or plywood), well jointed, Titebond 3 glue (waterproof when cured), piloted/countersunk screws, and then coat the inside with marine epoxy.

FWIW, I used West Systems 105 left over from a table project. Other than a very slow cure time, I think that this would work for short term water.

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My dad made wood trays with fiberglass lining several times. I don’t think they ever failed to be water tight. Usually they were trays for groups of indoor potted plants, and he liked to water infrequently, but heavily, so catching what came out the pot drains was critical. He usually used plywood bases, and fir sidewalls. But you can design it to inset the bottom in a rabbet around the edges so the plywood is hidden from the sides. If you are looking for some depth, the finger joints, or some router cut box joints, or even some biscuits would make the corners stronger.

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After reading up what Turkish marbling was I found a photo of the process. It’s looks they are using darkroom photo Developement tray…

After seeing this photo if you need something that’s easy to clean and is chemical resistant as well. Why not make something out of HDPE… I’ve made my own epoxy molds out of the stuff. It’s water tight won’t leak and easy to clean… only drawback it’s a little pricy at the moment.

Here’s an option on Amazon
Paterson 20x24 Developing Tray 1 #328 https://a.co/d/9UgTEvm

I don’t know how big you need but here are 8 x 10
Set of 3 Darkroom Print Film Photo Paper Developing Trays for Cyanotype Developing Fixing 8x10 Amazon.com