Sealing Wood

[Bob Akers]

Hi all, hope everyone is doing well!
I'm new to the sign / plaque business. I'm having trouble sealing the wood after engraving so the paint won't bleed out of the engraved letters.
I'm using clear pine at the present and have tried the following;
Shellac thinned 50 / 50 alcohol
Rattle can clear sealer
After sealer has dried 24 hrs, I then spray color of choice (mostly black)
let dry (24 hrs) then sand 60 grit ROS.
Just can not produce what I think I'm capable of. Good looking, but not
great.
What is the product / procedure of choice?
Thanks for any help!!
Bob

[Steve Schoene]

I''m not quite sure I understand what your problem is--where the bleeding enters in. Here's what I think I understand, and some questions I still have.

You engrave letters into the wood. What process, and how smooth is the surface?

Then you have tried to seal the wood using either shellac or a aerosol product of some sort. Shellac thinned 50-50 is very thin indeed. If you used Seal Coat it is only a little over .8 pound cut, and about 1.2 pound cut if you started with Amber or Clear Zinsser shellacs.

Then you spray paint into the letters. What kind? Brand and specific variety.

After the paint has dried you sand the surface with very coarse sand paper on an ROS. Why 60 grit?

At this point you aren't happy with the results. Here's where I really get confused. "Bleeding" suggests that the paint hasn't cured -- is that what you mean? Alternatively perhaps you mean that the paint has spread into the grain of the wood before drying and when you sand off the surface it leaves a "fuzzy" appearance? Is either interpretation correct?

[Mike Null]

Steve

What I think is happening, judging from my own engraving experience, is that even with sealing, the paint bleeds into the grain. This is far more noticeable on light colored woods. Even when you use seal coat and clear acrylic spray before color filling it sometimes bleeds into the surrounding area; what I call capillary action.

This is not something that can be fixed with sanding.

I have found clear lacquer to be the best sealer but still not foolproof.

[Steve Schoene]

That makes sense and was one of the things I was thinking.

I would think a more thorough sealing would be the answer. I wouldn't thin Seal Coat shellac. At two pound cut it will still penetrate quite well. I would still apply at least two coats--remember, some of the incised portion of the letters would be end grain, which would really soak up a finish. It needs to soak up the shellac so that it can't soak up the enamel. Three coats of fresh shellac could be applied within an hour and would be ready for top coating in another hour. I would choose the dewaxed Seal Coat over the Amber or Clear, which still contain the natural wax, as being a better surface for applying paint, particularly since so many enamels now contain polyurethane.

[Bob Akers]

Hi, thanks for the replies!
I'm using Ace brand rattle can black acrylic spray paint. I have also tried
enamal with the same results.
The 60 grit is just a starter to get the top coat of paint off. I finish with 220 which is fine for what I'm doing.
I'm engraving with a CNC router / V bit. The engrave letters are very smooth.
Yes the paint has spread into the grain. This is the problem I'm having issues with.
Black appears to be the worst color as I have done several house address signs with a couple of differant colors and little to no prep and have not had the problem.
I was not trying to fix the problem with sanding (just removing the unwanted paint from the top of the sign.
Attached is a picture of some address signs that I have done with great results.
Thanks again for any help!!!
Bob

[Rich Engelhardt]

Hello Bob,
I've done similar, but the lettering &/or design was hand carved.

Finish the piece with a coat (or two or three) of full clear material, then go back and apply the black by brush or wipe on.
Remove the excess from around the lettering with a rubber squegee.
I/we used to use a kitchen spatula.
Once the black has dried, then give the entire sign a coat or two of clear.

You'll have nice sharp lines without any of the "fuzzy" look.

And yes - you are correct. Black is the worst offender.
Black pigment is usually carbon. The carbon particles are insanly fine and work into even the smallest places.

[glenn bradley]

Quick clarification from Zinsser's site:
"SealCoat offers the timesaving versatility of refined shellac in a pre-mixed 2 lb. cut 100% wax-free formula."

I hit Seal Coat 1:1 with DNA for a large number of sealing jobs.

[Howard Acheson]

What I believe is happening is that the wood exposed by the router bit is, in effect, end grain wood along the sides of each engraved letter. End grain wood readily absorbs a liquid. Therefore, the colored finish you are applying into the letter is being absorbed sideways blurring the "crispness" you want to achieve.

As others have said, you need to more effectively seal this endgrain wood in each letter. You want to do it with a finish that is thick enough and impervious to the finish you later apply. Multiple coats of shellac would be my first choice.

Run some tests. Rout some letters and on a couple apply one coat of shellac, on some others, apply two coat and so on. Then apply your color material, sand and see which one works.

[Bob Akers]

Thanks to all of you who replied. I will take ALL advise and do some testing. I'm sure one or more of the comments will get me the results I'm looking for. Most customers preferr black.
I will cut a few samples and test tomarrow.
When I get the results I'm looking for, I will post my findings.
Thanks again!
Bob

[Bob Akers]

Hi all, hope everyone is doing well!
Well I had some time to do some testing.
Test 1 Shellac full strength three coats
Test 3 Sanding sealer full strenght three coats
Wood clear pine
After applying the above, I let it dry for 24 hrs.
I then sprayed painted the test with the problem black.
Allowed to dry for 24 hrs and sanded with 80 grit using a ROS.
The lettering that recieved the sanding sealer was the best (95%)
The lettering that recieved the Shellac was good (85%) but took much
longer to sand.
Thanks again for all the input!
Bob