Help! Outdoor sign bubbling

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Forum topic by mrs1thousand posted 03-24-2019 01:31 AM 1598 views 1 time favorited 21 replies Add to Favorites Watch
View mrs1thousand's profile


5 posts in 911 days

03-24-2019 01:31 AM

Topic tags/keywords: poly polyurethane epoxy finishes outdoor finishes

I made sign for a restaurant and finished it with an outdoor polyurethane and now it’s bubbling up very badly! It was hung outside their establishment and I don’t know if the sun hitting the sign caused it to bubble or what. I had trouble with it drying properly before giving it to them from the wet cold weather we had. I used an outdoor poly on it. Can this be salvaged? Also, what is a good finish for future reference for outdoor wood pieces?

21 replies so far

View bondogaposis's profile


6025 posts in 3562 days

#1 posted 03-24-2019 01:37 AM

Poly is not a good outdoor finish. Get something from a marine supplier. Avoid Helmsman spar varnish at all costs.

-- Bondo Gaposis

View John Smith's profile

John Smith

2994 posts in 1374 days

#2 posted 03-24-2019 01:37 AM

are you a sign maker by trade or a hobbyist ?
what kind of wood is it ?? it looks like construction lumber from the Box Store.
this appears to be out-gassing of trapped moisture in the wood.
did you also seal the back of the wood ? Like Bondo said – poly is not for outside use.
more info needed about the entire process in order to provide an accurate fix.
also a photo of the entire sign will be of some help.



-- I am a painter: that's what I do, I like to paint things. --

View Fred Hargis's profile

Fred Hargis

7183 posts in 3704 days

#3 posted 03-24-2019 11:04 AM

Bondo nailed it…urethane finishes are never good in the outdoors. As for salvaging it, you now have the urethane finish on it…and it will always be a problem. I suspect removal of what’s there (not what you wanted to hear) is the only solution.

-- Our village hasn't lost it's idiot, he was elected to congress.

View BFamous's profile


344 posts in 1332 days

#4 posted 03-24-2019 01:26 PM

If that sign was made out of standard construction lumber, it may just be easier to rebuild it than try to fix it. It looks as if the letters are recessed, which means you’re essentially going to have to remove the letters to remove the finish…

-- Brian Famous :: Charlotte, NC ::

View John Smith's profile

John Smith

2994 posts in 1374 days

#5 posted 03-24-2019 01:42 PM

yes, this appears to be a sandblasted sign.
IME; wrong material and wrong finish for any outdoor project.
Mrs.1Thousand, if you want to pursue this craft, there are a couple of
website forums for sign makers that are run by sign makers.
my honest opinion would be to leave this sign in place while you make
another one with all the correct elements: wood, primer, finish, hardware, etc.

and to accurately answer your question: Can this be salvaged?
no – it can not.



-- I am a painter: that's what I do, I like to paint things. --

View mrs1thousand's profile


5 posts in 911 days

#6 posted 03-24-2019 02:35 PM

I make laser cut and engraved signs. I’ve never done anything requiring a finish quite like this. So the letters are engraved and backfilled, then it was stained and the outdoor poly was used for the final finish. I’m concerned I won’t be able to sand this all the way back down especially since the letters are recessed. If I do sand it back down, I’m going to try to lightly hand sand the recessed letters and use the marine outdoor finish. I’m sick to my stomach about it because this sign took 3 hrs to engrave on each side.

View mahdee's profile


4291 posts in 2979 days

#7 posted 03-24-2019 02:49 PM

Get a can of gel paint stripper and follow the instructions. Use a toothbrush on the letters and brush the whole thing with mineral spirit. Wipe it down, let it dry and sand if needed (it will need it).


View GR8HUNTER's profile


8861 posts in 1924 days

#8 posted 03-24-2019 03:19 PM

set up small trim router with bit to clean up letters just a bit deeper then what they are at then paint it then send whole sign through wide belt then put proper finish on it done should only take a day or 2 lesson learned :<))))))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN :<))

View BlueRidgeDog's profile


884 posts in 990 days

#9 posted 03-24-2019 03:26 PM

My view is not so draconian as the others, strip it and refinish. Personally I would use a breathable oil finish designed for outdoors (the popularity of decks has caused them to proliferate).

View John Smith's profile

John Smith

2994 posts in 1374 days

#10 posted 03-24-2019 05:07 PM

if you plan to produce such exterior signs in the future, there are a couple
of sign maker forums that have members “crossing over” from the Old School
into the new with CNC and Laser engravers.
using the correct finishes can keep you out of the pain and misery section.
just be aware that using construction grade lumber and the wrong finish is
a recipe for disaster right from the git-go.
there are several varieties of wood that will serve you well for outdoor projects,
redwood, mahogany, teak, loqust, cedar, cypress, to name a few.
yes, they cost more than utility grade pine. you get what you pay for.
also – most clear finishes are not designed for the “one time & forget it” projects.
varnished and clear coated projects need to be sanded and refinished every couple
of years. so someone needs to take on that responsibility to ensure a long lasting
and good looking sign.
also – a wood that will darken with age and exposure to the elements will be very
hard to read from a distance with dark colored paint.
Best of luck in all your endeavors.



-- I am a painter: that's what I do, I like to paint things. --

View Snipes's profile


459 posts in 3456 days

#11 posted 03-24-2019 05:29 PM

While it may be easier and more efficient use of time to just make a new sign. Salvaging that sign is definitely possible. You could probably use heat gun and remove that poly, or planer or sander to remove raised portion. I agree using an outdoor wood is ideal, I’ve seen many a signs built out of pine, basswood, elm, plywood, all of which last with proper finish and or ability to dry.

-- if it is to be it is up to me

View Andybb's profile


3329 posts in 1815 days

#12 posted 03-24-2019 08:04 PM

Normally I’d say to just rebuild it but it was done for a paying customer who needs a sign outside of their establishment. From a customer service aspect I think you’d want to tell them you will make another sign for them ASAP and apologize profusely. Their customers might not notice the bubbles but they will comment on a missing sign which will only further irritate the owner. Then use the knowledge gained from this thread and get to work on an even better sign for them.

-- Andy - Seattle USA

View bruc101's profile


1502 posts in 4753 days

#13 posted 03-24-2019 08:20 PM

I’ve been hand carving, router cutting and sandblasting commercial wood signs for 40 years.

I use vertical grain redwood for sandblasting, Cypress for hand carving and router cutting.

I seal the redwood to keep it from bleeding thru the paint and use only acrylic latex semi glass paint and primer with nothing on top of it. The only thing I seal is gold leaf, other than the redwood.

Never had a failure and the paint usually holds up real good for about 10 years.

As mentioned by other posters, find a sign makers forum if you plan on doing this as a business. Youtube may have some good videos also.

-- Bruce Free Plans & Calculators

View mrs1thousand's profile


5 posts in 911 days

#14 posted 03-25-2019 12:51 AM

Good news! I have a friend that sanded it all the way back down to the natural wood which looks perfect. So tomorrow I am engraving it then will use a sand and seal on it then a marine varnish to seal it. I think I’ve learned a lesson on this one.

View John Smith's profile

John Smith

2994 posts in 1374 days

#15 posted 03-25-2019 01:11 AM

I still have a couple of questions:
what part of the world is this sign going to hang
and – what kind of wood are you using.
a marine varnish such as Pettit or Epifanes requires a minimum of
6 to 8 coats to be effective against the UV which breaks down the finish.
Minwax sanding sealer is not a good foundation for marine spar varnish.
every couple of years, it needs to be lightly sanded and a coat of varnish applied.
best of luck in your project



-- I am a painter: that's what I do, I like to paint things. --

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