Particle board with a few coats of something to waterproof it
2015 December 28 Tech Workspaces & Tables
In another article, we looked at a couple of work-table ideas.
Worktables with plank-tops don't really need a finish. Usually they can be left in their natural state, unless you really like wood finishes.
With particle board or MDF, it's different. These materials can't withstand moisture.
Let's take a quick look at some possible finishes.
I'm not a pro woodworker, and this is not an exhaustive guide to every possible finish. Like many of you, I'm just a guy trying to build useful stuff with the least amount of time and expense... while still having something that's durable and doesn't look too rough.
With that in mind, let's see what we've got here.
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In This ArticleWhen To Apply A Finish
When To Apply A Finish
Many workbenches don't need any finish at all. Plank-top workbenches develop character when they slowly oxidize and acquire all those scuffs, saw marks, etc. When I've built workbench tops out of 2x10 planks, I don't think I ever applied any type of finish.
There's nothing wrong with applying a durable finish to a plank-top, but it's not 100% necessary.
On the other hand, some types of surface-- especially particle board and MDF--cannot withstand the usual spills. One afternoon out in the rain, and they're toast. Anywhere you get a lot of water, such as from a flood, is not a good place for raw particle-board or MDF.
Both particle and MDF will absorb liquid like a sponge. The edges are the worst for this.
When you think of wax, you might think "water-resistant."
Actually, paste wax is not a very good barrier against water, unless you put down a very thick layer. A thick layer of wax on a particle board top... haven't tried that, but it just doesn't sound like a good finish for this material.
Paste wax can look very nice on well-sanded hardwood, but it's really meant to be used on top of an existing finish, such as shellac. For that use, it's brilliant; every woodworker should have a can of paste wax. I like this stuff; it's not expensive, and it looks fantastic when used on a varnished surface.
On the opposite end of the spectrum is oil-based polyurethane varnish. A few coats of this stuff, and you've got a finish that's like solid plastic. A glossy polyurethane finish looks beautiful if you do it right, and it's highly water-resistant.
For workbenches, there are two main drawbacks.
One, the finish reduces friction. You might find that you'll need to clamp stuff more often, just to keep it from moving when you work on it. There's definitely less friction, but I've found that the poly-coated surface is still highly usable.
The other problem is wear-and-tear. A clear poly finish doesn't look so good when it's all nicked and dinged up. To repair the finish, you end up doing a lot of sanding and re-coating. It can be done, but it's work. Here again: maybe not that big a deal.
Oh, and third: particle board will soak up a lot of polyurethane, using it up faster. That might be an advantage for durability, though. If the polyurethane sinks way down into the grains, the finish is probably not going to lift or peel away.
Despite its possible drawbacks, I still use polyurethane to seal particle board. (The edges take up too much of it, though, so keep reading to see how I fixed that.)
If you think your work table could accidentally get left out in the rain, polyurethane is probably better than anything else, with the possible exception of marine epoxy, which I haven't yet tried on particle board.
Old-time finishes were often made of shellac. Fine woodworkers still prefer shellac for some things. There's nothing quite like it.
Shellac finishes look great, until they get some water damage. Their water resistance is poor to mediocre.
Some people do use shellac to seal the edges of MDF or particle board, but it seems they apply something else as a final coat. One coating of polyurethane over the dried shellac would probably work. I haven't tried this.
Actually, this product is shellac-based, and it's designed to do exactly what we're talking about: seal the wood, so you can sand it and then put another finish on top of it. Such as, polyurethane. And the nice thing is, it dries very quickly, so you can get to sanding.
Next time around, I think I'm going to try this.
I've already found stuff that works for particle board, I'd probably save the varnish oil for plank-top furniture.
Anything with extra thinners is only going to make the particle board soak up more of it. That means you'll waste more of it, and spend more money.
The idea with particle board is to fill the edges with something that dries very solid. It makes sense here to use something like a polyurethane or a glue-like material.
What is varnish oil, anyway?
There's a drying oil (such as polymerized linseed) mixed with some type of wax or resin. It's this wax or resin that provides the "varnish" qualities. Copal (a dried pine resin) is an example of an ingredient that's sometimes put into "varnish oil". There's also usually a thinner.
There are a number of products that would probably qualify as "varnish oil".
Any "tung oil finish" is probably going to be a type of varnish oil. It's probably not going to contain any actual tung oil, unless you buy 100% tung oil. Which means it wouldn't really be "varnish oil" anymore. It would just be a slow-drying oil.
Pre-made "Danish oil" products are also going to be varnish oil, mostly. Danish Oil is another imprecise term; there are many different formulas with all different drying times and other characteristics.
Tried & True Wood Finish is great stuff; I don't know if it's technically a "varnish oil" though. It's got the drying oil (polymerized linseed) mixed with beeswax. Tried & True also makes an actual "Varnish Oil" product, though I haven't tried that yet. If you are into woodworking or just making cool stuff, give their finishes a try.
These varnish-oil-type products are good for finishing plank tops. For particle board, other things would probably work better.
Elmer's has a new wood glue that's waterproof and sandable.
I tried carding this wood glue into the surface of a particle-board top. It seems to work well.
There's one caution. A single coat is probably not enough. Some areas will not get enough glue. You will not know which ones, until you apply the polyurethane coat.
As the poly sinks into some areas of the wood and not others, you will see the mottling...
Should have applied two or three coats of glue, not one.
It will dry that way. You can salvage it, but to do that you'll probably have to sand it all down & start over. That's what I did.
Before you apply any polyurethane, do at least two coats of wood glue (if you're going to use wood glue). Use a spackle knife that's 3 to 4 inches wide. (I have to stop calling these "putty knives".)
I have a super-cheap one, but lately I've been wanting this one that's made in the USA. Whatever you get, I suggest a blade that's three or four inches wide. Flex-blade or not, either should work OK.
It's fairly easy to wood glue the edges of the particle board. I was able to glue three edges at a time. Set the whole thing upright on newspaper or something. Here, you'll definitely need three coats at least.
Wood Glue Max is pretty great stuff; if you use it to seal much particle board, I would get the gallon size.
I don't know how well the wood-glue method holds up long-term, but once you have a coat of polyurethane on it, it ought to last. Oily finishes cause wood glue to get weird, but this shouldn't happen with polyurethane. It dries like plastic.
A straight polyurethane finish might create a better bond, but I'd at least prefer to be able to seal the edges of the board with wood glue. It just wastes too much poly, otherwise.
Putting a wood finish on a work table is usually optional. However, particle board or MDF will last much longer if you seal them against water. Unsealed, these surfaces can go bad in a matter of hours. All it takes is one rain.
This has been a look at some wood-finishing materials. If I had to pick one finishing material for particle board, it would be this stuff. I would also recommend getting a gallon of this, because it's handy for so many things (not just particle board).
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