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Discussion Starter · #1 ·
Really a 'finishing' question, not a routing question, but ask the experts…

Problem: Painted letters are blistering.

This is my first try at making signs – two slabs of very dry cherry cut from same stump a few year ago.
Cut letters into wood 3/16” and sprayed with Rustoleum Gloss Protective Enamel. Two coats and although I tried to be 'thin' it did seem that paint got thick on bottom of cuts. Sanded off surface, brushed on 2 coats Zinsser clear coat then 4 coats McCloskey Marine Spar Varnish.
Very happy with finished signs for my first run, however after putting them outside (40-50F and rainy) for about a week the blistering on letters appeared. The finish on the bare wood is just fine.
Pictures of the two signs and closeup of a blister attached.

Any thoughts on what went wrong and what I should do different next time?
 

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Hey, Chiselhead; welcome!
I love the font! Beautifully created.
My thought on the paint is that because the wood wasn't sealed first, the spray enamel has allowed moisture in from the back and any bond that existed has been broken by hydrostatic pressure. All it takes is a tiny bit of vapour plus the sun on it and bam, blisters.
That used to be a huge problem with exterior oil paint on older homes, especially on the exterior of bathrooms and kitchens; the water vapour (humidity) on the interior exfiltrated to the underside of the basically waterproof paint on the outside wall and like evil magic, blisters. With the introduction of interior vapour barrier, and breathable coatings, the problem has almost disappeared.
The sign guys here will likely give you more practical advice on how to avoid this issue. Maybe black ink? The gloss will come from your top coating anyway.
Again, great artwork!
 

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Oliver (Prof. Henry)
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Tracking down the answer to your problem may be better left to some of the expert finishers here, but I can suggest what I do on my signs. First, after carving I generally seal the sign with shellac on both sides. Next if I am spraying the color into the letters I use primer rather than paint. It dries quicker and is easier to sand off. The final coat of gloss varnish (I use urethane) will make your letters glossy like the rest of the sign. I wonder if the first coat of paint you applied to the letters was completely dry before you applied the finish coat, especially where it was thick, and that the paint is off-gassing and causing it to bubble. Another solution for signs is to use Nova Color sign paints which are water-based acrylic and dry quickly while having a lot of color-fast pigment. They work well under a urethane finish.

Even with your minor bubbling issue, the signs look great. The live edge really sets them off.
 

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David
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Welcome to the forum! When you get a chance go ahead and complete your profile with first name so we can address you that way. Your locations would be helpful, as well.

I agree with Oliver and Dan - those are very good looking signs! Both suggestions are likely as to the cause and they may settle down after a bit, ya' just never know.

David
 

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Discussion Starter · #6 ·
DaninVan -> Font is Carolingia. I WISH I had a CNC... I just printed on paper, cut out letters and traced onto wood, then very new-guy-slowly cut them out by hand. I did create some of the capital letters myself. For example the Carolingia capital H is a goofy enlarged lower case h that I didn't like. So I did a little graphic editing to make a proper H with curves that match the font.

All -> Thanks for the comments. I suspected perhaps I was inpatient and did not let the thick enamel spray dry enough. Next time I'll use a primer spray and wait.
 

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Ross
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Welcome to the forum.
 

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Really a 'finishing' question, not a routing question, but ask the experts…

Problem: Painted letters are blistering.

This is my first try at making signs – two slabs of very dry cherry cut from same stump a few year ago.
Cut letters into wood 3/16” and sprayed with Rustoleum Gloss Protective Enamel. Two coats and although I tried to be 'thin' it did seem that paint got thick on bottom of cuts. Sanded off surface, brushed on 2 coats Zinsser clear coat then 4 coats McCloskey Marine Spar Varnish.
Very happy with finished signs for my first run, however after putting them outside (40-50F and rainy) for about a week the blistering on letters appeared. The finish on the bare wood is just fine.
Pictures of the two signs and closeup of a blister attached.

Any thoughts on what went wrong and what I should do different next time?

Hello and welcome. Both signs are really great. As for your paint issue, I think like others it's wet wood. Even wood that is air dried only gets down to around 14%. A lot depends on the wood and thickness and how long it's been drying. I do think you might be right about the paint puddling in the bottom.
 

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Welcome to the Forum ''Chisel Head ''

Nice signs, finishing is a learning process that takes some time but worth the investment for it's the first thing we see on any project. I'm sure you'll find the solution and continue to make nice signs.

Dan
 

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I use flat paint to color the letters. I am guessing that Rustoleum enamel does not allow air and gasses to pass through it, which would of course create a "balloon" that the gases could inflate. If you want to coat the whole thing in a thick plastic coating, you should allow time for it to breathe. I would not coat it right away after cutting the wood.

Joe
 

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Discussion Starter · #13 ·
DaninVan: I bought a inexpensive 5amp handheld Rigid at HD and used a 1/8" straight cut bit for one sign and then bought a little nicer Amana tapered bit (Amana Tool 45776 Solid Carbide 30 Degree Engraving 0.060 Tip Width x 1/4 SHK x 2-1/4 Inch Long Signmaking Router Bit) for the second sign.
 
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