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By porker
I'm making some house signs out of oak reclaimed from an old staircase my neighbour ripped out. I have routed out the letters but want to know what the best paint would be to colour the letters? I plan to finish the sign in Osmo UV oil as I have a tin. I made a sign for myself earlier this year and just used an aerosol of black car paint I had in the garage to colour the letters and finished with Osmo. It turned out OK and looks fine a few months on but as these are for other people I want to use the right stuff. Another thing I did was route these out with a thin straight bit rather than previously using a v bit. I have rounded over all the sign edges because I read that protective finish tends to fail on sharp edges. Have I made a mistake using a straight bit to route the letters as the outline of the letters is quite sharp?
Thanks Matt
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By ED65
porker wrote:Have I made a mistake using a straight bit to route the letters as the outline of the letters is quite sharp?
I believe they'll age less well than if carved out using a V-shaped cutter yes.

Any exterior-rated paint can be used on wooden signs although obviously there'll be some variation in maintenance schedule. The fans of real oil paint (one should be along shortly) will swear you'll get the best durability, and the best weathering characteristics, if you use that but I remain to be convinced that it's the only paint worth considering. I think casein would actually provide the maximum lifespan assuming you can get it of course.

In terms of standard off-the-shelf options that don't cost an arm and a leg, I've seen very good results achieved using oil-based enamel paints. The 'secret' is to paint the first coat on well thinned so it soaks into the wood, the following coats thinned not as much to a sort of creamy consistency and no thicker.
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By AndyT
I don't think I have any pictures of it, but I made a sign for a friend a few years ago. Like yours, it was oak, with the letters carved into the surface.
I wanted to colour in the lettering to make it more visible. I happened to have a little tin of cellulose matt black paint which I had bought way back from a car parts shop, to touch up the rust spots on my car's bumpers. Using a thin artist's brush, it was easy to apply and it didn't bleed into the surrounding wood. It dried very quickly.

Several years on and the untreated sign has weathered to a nice grey but the black is still clear.
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By custard
ED65 wrote:The 'secret' is to paint the first coat on well thinned so it soaks into the wood

Absolutely not. If it's thin enough to soak into the wood then it will bleed into the background, beyond the carved lettering, and ruin the job. Bleed is the mortal enemy in sign work; you can always scrape, sand or plane to remove paint that's gone over the edge, but once it's soaked into the fibres then you're stuffed.
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By custard
Here's a photo that illustrates the risk of bleeding,


this was a fade test using dyes. The dividing lines were marked out with good quality masking tape, but that didn't stop the dye migrating. Contrast that with masking off the outer sections for a coat of Osmo, where there's no bleed at all.

In this context it doesn't matter in the slightest, but with your sign it would be ruinous. The last thing you want is paint thinned down so it'll soak into the wood.
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By Droogs
Rather than paint, have you thought of gilding with gold leaf. It is really easy to do and once rubbed up will last far longer than paint
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By porker
Thanks all for the suggestions. Very helpful. I now have a small pot of black enamel so I'll give that a go. I may also try to take the sharpness out of the letter edges which I think I will have to do by hand.

I like the gold leaf idea and would love to give that a go on a future sign. The oak I have though is quite pale and I'm not sure whether I would get the contract I am after. I do though have some bits of old lab bench top which is some sort of oily iroko type hardwood. I think gold leaf would look great with that.