But we want to keep the coffee stain
April 26, 2016 10:06 PM   Subscribe

We are currently in the process of remodelling our bookcases, which includes having stripped back the original stain (using a hand plane) and now restaining them. The timber is relatively cheap pine. We have been experimenting using instant coffee as a stain and we like the look. However searching for information on how to seal it is resulting in every website saying you MUST do xyz, and all these musts are completely different.

Our preference is for oil or wax, but we are willing to go chemical varnish if that is what is really required. Essentially we need to seal the stain so that it doesn't transfer (on to the books that will be sitting on it mainly) or attract insects, or fade dramatically.
posted by Megami to Home & Garden (10 answers total) 4 users marked this as a favorite
I'd seal it with a clear polyurethane.
posted by humboldt32 at 2:54 AM on April 27, 2016 [1 favorite]

If you don't like the idea of a chemical sealer, the main difference with a natural oil (like natural tung oil etc), and an optional covering with wax, is the time that you'd have to let it dry. Think two weeks or so. But you'd be fine after that. I'd use poly on a coffee table or something, but for bookcases you can definitely go for an oil that doesn't require that kind of durability and gives you a deeper, soaked in beauty.
posted by transient at 3:58 AM on April 27, 2016

...or fade dramatically.

I haven't had reason to look into coffee as a wood stain, but if it's inclined to fade over time then no topcoat is going to prevent it from doing so.

Can you say more about your desire to avoid a "chemical" varnish? Is it concern over VOC's? Dislike for the look of a heavy film finish? Maybe just a vague crunchy-granola sensibility? Knowing your priorities would help narrow the range of possibilities.
posted by jon1270 at 5:14 AM on April 27, 2016

Minwax polycrylic is water-based, inexpensive, dries quickly, and doesn't smell very much- I've used it indoors and find it very inoffensive. Best to let it cure for a couple days before putting books on it, but it definitely cures faster than most topcoats including oils.

It's pretty easy to apply- I'd say it works best with a silky synthetic brush (doesn't need to be an expensive brush though, just one with soft longish bristles), and don't over-brush it or it'll get a bit gloopy and the water in it might dissolve and lift your coffee stain. Practice on a hidden part of the bookshelf first before you do the sides where the brushwork will show.
posted by pseudostrabismus at 6:14 AM on April 27, 2016 [1 favorite]

Coffee is a plant based material and not ideal for lightfastness or tint strength. If you like that color, you can get consistent effects with earth colors, which are the pigments used in commerical paint applications. Closest color to coffee would be burnt umber, and can be purchased inexpensively in water color, oil or acrylic and hand mixed into the wood or into your binder for a custom effect.
posted by effluvia at 6:24 AM on April 27, 2016 [1 favorite]

My current preference is for shellac.

Polyurethane is sometimes evil.
posted by yesster at 7:10 AM on April 27, 2016

You might look up UV resistant finishes. I'm not sure if they relate to the strength of the finish or the ability to "block" UV from bleaching the wood or stain.

If you are against lacquers or polys, try something like Watco Danish oil. It's a oil, varnish mix, that you basically wipe on, wait wipe off. Will polymerize and with repeated applications will provide a durable seal.

I should also add that once any modern finish cures, it's generally non toxic, and many finishes cure pretty fast, like days not months fast.
posted by Max Power at 7:45 AM on April 27, 2016

I have used and loved Earthpaint products.
posted by slipthought at 7:51 AM on April 27, 2016 [1 favorite]

It really does depend on your priorities, as jon1270 asks above.

If you want to use oil, then danish oil or similar will be fine. If you are going to use danish oil though, why not just use a danish oil than contains stain as well and avoid the whole instant coffee issue? I'd be concerned with any finish applied on top of instant coffee that they might mix together with undesirable results.
posted by ssg at 9:04 AM on April 27, 2016

Summary first, because I typed this up and realized that it's way too long:
1. prefer no coffee, but if coffee
2. avoid water-based varnishes (polyacrylic, etc.)
3. shellac is a good choice if you're okay with the work and trade-offs
4. good old varnish is, as often happens, a very good choice for home finishers. A wiping varnish is friendliest to new finishers (and bookcases don't suffer abuse like a tabletop).
5. wax is a fair choice if you're okay with the work and the trade-offs


Coffee's color is part dye, part pigment. The dye parts are notoriously not lightfast. The pigment parts are sort of lightfast. Humidity and real air exposure (ozone, etc.) will add to the problem. You'll experience uneven, very heavy fading and a notable color shift as the piece ages. As someone who has been finishing furniture for a long time, I strongly recommend not using coffee unless you want to be doing this again in a couple years.

(I don't have real test numbers for coffee but, as a general rule, extremely few natural dyes come in better than BS 4. BS 4 means you're definitely going to notice the fading over the years. Coffee likely rates even lower than that.)

If you want to stick with the coffee rather than replicate it with stable dyes and pigments (totally doable!), my general advice would be to stay away from finishes with a significant proportion of water because you'll find they tend to re-dissolve the stain layer and then you end up with 1. blotchy/smeared stains and 2. a topcoat that's picked up a color and is now slightly opaque. It's sometimes possible to get a decent water-based polyurethane finish overtop water-soluble dyes but it takes practice.

You may also find that the denatured alcohol in shellac will smear the stain but that will just take some experimenting. Wipe some denatured alcohol on a hidden spot as if you were finishing the piece and see what happens. I'm not a big fan of shellac for something like a bookcase because french polishing pieces of that size is a real PITA and I'm lazy. It's a lovely and repairable finish, though.

My choice would be a traditional mineral-spirits-based varnish: urethane or "oil." (See my old ask comment on why "oil" in the finishing industry has practically nothing to do with oil; they're practically all varnish-oil mixes. Because oil is a terrrrrrible finish.) Test it before committing to make sure it won't displace or dissolve your coffee stain. Despite my earlier comment about lightfastness, I'd suggest avoid varnishes which claim extra UV protection (spar varnish, etc.) because 1. modern varnishes are all pretty decent at this and your bookcases aren't going to sit outside, and 2. varnishes that focus on UV protection often cure "soft."

The wax you mention is a reasonable option, too. It'll show scratches and doesn't offer much in the way of protection, but it's a heck of a lot better than nothing. Beware of its softness, though, because even with a very hard wax some books / pieces will eventually slightly "stick" to it (basically sink in very very very slightly and displace the wax) because they sit in one place forever. This may be manageable depending on what you're using the cases for. Be careful in handing wax finishes because they're definitely not harmless during application: the wax is usually slightly dissolved in something like naptha so you can actually apply it. As with varnishes, that stuff evaporates and leaves a safe finish, but be careful.
posted by introp at 12:55 PM on April 27, 2016 [1 favorite]

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