Polyurethane on Acrylic Paint

[funkypandamonium]

Hi,

I recently painted a design in acrylic paint on a piece of maple wood that will eventually be subject to elements such as UV, weather, foot traffic, etc. I've heard that marine polyurethane is the way to go to protect this sort of project, but I'm having a heard time finding one that is water-based and would not smear my acrylic paint. Is any water-based polyurethane (I've found some with UV protectant) going to do the job?

Also, what are the benefits/features/differences of matte, satin, and gloss?

I've found quite a few water-based polyurethanes at this site:

other suggestions for this project are greatly appreciated. This is what I've painted for those interested (it is the platform on the top of the trailer).

Cheers, A

[BDBConstruction]

You are going to have slim pickin's for water based exterior and my guess is you may be hard pressed to find much other than gloss. Zar makes a water based exterior poly and I think it may be available in gloss only but not sure. Most water based poly's just dont have the ability to stand up to exterior use and especially UV. The finish is less of an issue but the gloss finishes tend to be less pourous and therefore better for exterior applications. You may find some matte varnish at an art supply store or on the net that would handle exterior with several coats (usually 6-10)

Mark

[funkypandamonium]

Mark,

I've heard some folks say that an oil-based polyurethane won't harm acrylic paint if as long as the paint is completely dry. But other's have said it will smear or crack the acrylic.

Any thoughts?

[Artemus]

This is a common problem when applying finishes over stains too. The solution there has been to apply a coat of shellac first to seal the stain, then apply the poly, varnish, whatever. Art

[Father Haskell]

Shouldn't smear. Acrylic is no longer soluble once it's dry. Test on a piece of scrap if in doubt.

[Bonehenge (B A R R Y)]

It shouldn't, but it will yellow it.

You can almost always prevent two unknowns from interfering with a barrier coat of Seal Coat (brushed or sprayed) or sprayed aerosol Clear Shellac. Either will go under anything, and over anything.

[J. Clarke]

If that "Cheers" indicates that you're in the UK then you're in luck--in the EU there's a product called "Sikkens Autoclear WB", a waterborne automotive clearcoat. Good luck finding it in the US though. duPont supposedly has a similar product.

I suspect that it's expensive and it's a multipart system, but it should last as long as any other automotive paint.

[funkypandamonium]

If I apply the Seal Coat, will the polyurethane still create a yellowing effect?

[Tanus]

Flexner has an article in this month's Popular Woodworking that addresses that very question.

"Almost any finishing product - stain, filler, glaze, finish - can be applied successfully over any other finishing product, except wax, as long as the product is dry."

Dryness seems to be the real key here, and depending on the bottom coat, it may be days or weeks before it's truly dry.

Popular Woodworking, Feb. 2008, p. 92

[J T]

Tue, Jan 29, 2008, 3:35pm (EST-3) [e-mail] mumbled: Hi, I recently painted a design in acrylic paint on a piece of maple wood that will eventually be subject to elements such as UV, weather, foot traffic, etc. I've heard that marine polyurethane is the way to go to protect this sort of project,

You guys never cease to amaze you. I'm gonna call all the 1-800 numbers on the cans and tel them to stop putting it on the labels, because no one calls them anyway. Now me, if I had a question like yours, I'd call the all the 1-800 numbers i could and ask them. But that's j ust me.

JOAT

10 Out Of 10 Terrorists Prefer Hillary For President - Bumper Sticker I don't have a problem with a woman president - except for Hillary.

[B A R R Y]

Yes. The yellow color is in the oil poly.

The barrier coat of dewaxed shellac (aka Seal Coat) is to prevent one product from interfering with the other. If the sealer is going over something that may be disturbed by alcohol, like lettering and certain dyes and stains, it should be sprayed. Luckily, Zinsser Clear Spray Shellac is dewaxed, cheap, and handy.

If you possess the acrylic paint and the poly, you can make a test panel that may prove the barrier unnecessary.

I've been bitten in the ass enough times that I use a barrier any time I'm not absolutely positively sure of the final result.

I've also learned that test samples take far less time than repairing and redoing the actual work, so I always have time to test if I'm not positively sure of the outcome.

[BDBConstruction]

Many times calling the 800 number is an absolute waste of time as you get someone who has been briefed in the HGTV aspects of the product not the real technichal aspects. Additionally you will only get the textbook answer and never any creative or outside the box answers. The will also never say "well, our product will not work in that application but her is a phone number to our competitor, they do have a product that is just what you are looking for". I have had some troubles with minwax polycrylic in the past in homes with forced hot air heat and calling the 800 number was a total joke.

A far more successful tact is dealing with a reputable supplier who deals with the nitty gritty of the product on a daily basis. They hear daily from dozens if not hundreds of individuals and proffessionals who work with the product. They also, through direct experience, know what is really possible and what will and will not work with a given product regardless of what the label or the 800 number says. A good supplier will be more than willing to say "I dont have what you need, but there is a place across town that does, let me give them a call and get you in touch with them".

I can think of dozens of things we do with finishes that the MFR would expressly tell you not to do and they work day in and day out.

Mark

[J T]

Wed, Jan 30, 2008, 11:25am (EST-3) [e-mail] (BDBConstruction) doth sayeth: Many times calling the 800 number is an absolute waste of time as you get someone who has been briefed in the HGTV aspects of the product not the real technichal aspects.

That's when you ask to talk to someone that actually knows what he/she is talking about. I've never had problems getting usable info, even being told on occassion I'd have to try somewhere else. I've never had problems with being switched to somene with real knowledge. All you have to do is be polite, and ask.

JOAT - who does not welcome thread question e-mails..

10 Out Of 10 Terrorists Prefer Hillary For President - Bumper Sticker I don't have a problem with a woman president - except for Hillary.

[dgadams]

Several of the acrylic paint companies make varnishes for protecting acrylic paintings. Golden is one company that comes to mind.

web-site also has a lot of information. Might be worth a look.

D. G. Adams

[B A R R Y]

I'm guessing by trailer, you mean rear rack.

Now that I see the project, I think I'd stick with a marine varnish, with the barrier I've mentioned earlier, between. Marine varnish will stand up to the elements very well, and a little "ambering" won't hurt the overall look. It's already got a touch of amber to it.

I work in a bicycle shop, and most all of the wood parts on cruisers and commuters seem to be covered with a tough, exterior varnish.

I see what looks to be a Cateye LED lamp on the front fender, but what's the box on the h-bar?

How does the bike handle with such a long wheelbase? Is it like riding a tandem with no stoker?

Great looking project, though! I love odd bikes!

---------------------------------------------

** **

---------------------------------------------

[funkypandamonium]

Barry,

The bike in the picture is a FreeRadical Xtracycle (check them out on Xtracycle.com). The long wheel base allows for more stability and the Xtracycle is much better than any rack or other bike trailer you will come across.

This bike pictured isn't actually my bike, that is one I found online that had the best photo showing the whole idea. However, mine is just the same, only a different bike. What you see in that picture is the standard finish on the 'snap deck'. I sanded down the finish and painted a design with acrylic on that.

Thanks for the advice!