Polyurethane clear coat

J

Jason Shore

Guest
I am in the process of clear coating a laminated stock with polyurethane.If any of you guys have used polyurethane how many coats did you apply on your stock ?
I have been doing light coats.
Any imput appreciated
Thanks Jason
 
Two differ blends

I found two Urethane's on the shelf. One recommended for Indoor only and the other for Indoor/Outdoor application. Made by Minwax, Helmsman Spar Urethane is for Indoor/Outdoor use. Comes in Clear Gloss or Satin Finish. The other Is just plain Polyurethane, and is only for indoor applications. Proper wood preperation is a must, regardless of which one you use.
 
I have a laminated stock from Steve Mcgee which I haven't finished yet. Most of the suggestions I've received are to use automotive clearcoat on laminated stocks.
 
The pressure laminated birch stocks are nearly impervious to any finish soaking into the wood very deeply. I tried finishing my first one with a sanded in oil finish and it looked great until I hunted Idaho elk in the rain and all the grain raised up. I now use satin polyurethane with generally 5 to 6 coats wet sanded between coats. The wet sanding is necessary because no matter how well I think I have block sanded the stock to a dead smooth surface, the material always ends up with tiny dimples the size of pin pricks that need to be filled with finish. I do the last two coats without sanding to ensure a good depth of finish.
 
There's a big difference in the polyurethane you find at the local home center and what's used in the automotive industry. Minwax and others do not require a catalyst for hardening, they are an air dry product. Automotive polyurethanes use a catalyst to chemically harden, these are also more resistant to chemical and surface abrasions. Automotive urethanes have a higher gloss and should be sprayed on. Two coats should be plenty, this will give you about a 2-3 mil thickness that can be color sanded and polished out.

Here's a Packawood stock I made that has been done with automotive clear polyurethane and color sanded.

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Rembrandt,

Beautiful stock! That is the sort of finish I want to try on a stock project I have in the works.

I have a 25gal 140psi air compressor and a small gravity-fed HVLP conversion gun... what else does a person need for hardware? Hopefully in the next couple weeks as I get some time off during the week finally I plan on swinging by a couple local auto paint suppliers and seeing what they have (starter kits, maybe?).

I've heard other people refer to having a body shop do it on the side... not sure if they do the between coats sanding (is it necessary with auto clear coat) and how much that would cost on average?

TIA,

Monte
 
If you are only doing one stock, do the sanding and prep work yourself and take it to a body shop for them to spray it. They can shoot the stock while spraying clear on a repair job or an overall finish. If they have a baking system that will be to your advantage.

Buying the materials yourself will be a lesson in sticker shock....automotive paint stores sell the materials in minimum quantities of quarts. You'll end up buying enough catalyst to do an entire car as well more reducer than you'll ever need. Don't be surprised if you end up spending a couple hundred on just materials. The last car I shot was about $1200 in materials. Did I mention that the materials are a petroleum by product?....just like fuel prices the stuff is expensive.

Color sanding after it's painted is what makes a nice paint job a great paint job. This takes out any texture (or dust) that's in the finish and makes it look like glass. Sanding in between coats is not necessary, you're only concerned with the outer layer of the clear. Start with 1000 grit paper, go to 1500 then finish up with 2000 grit. Finish the project by buffing (machine polishing) the surface to a mirror appearance. The other advantage to this is it reduces the millage thickness of the material and reduces the risk of chipping. You only want enough clear to get the shine and protect the wood.
 
I am getting ready to finish a laminated stock but I prefer more of a satin finish rather than the high gloss. Can you do that with automotive clear coat? If not what can one use?
 
To get a satin finish with an automotive urethane, add what's called a "flattening agent"....the more you add the less gloss. A satin finish should not be sanded or polished. Another trick to get a satin finish from a gloss urethane is to scuff the clear down with a fine steel wool. (000 or 0000)
 
Rembrandt

I'm not familiar with the term "color sanding", could you explain please? I have a laminated stock from Steve McGee that he recommended be finished with automotive clear coat and I'm wondering about all that would be needed to do the job. Type of spray gun, respirator, spray booth, etc?
 
Be careful with having a body shop spray the automotive clear coat on your wood stock. Most use a heated spray booth to cure the finish and it really gives it a nice glassy smooth finish. The problem comes from heating the wood. This will cause water vapor in the wood to escape, leaving large blisters in the finish. It is horrifying to see this on your carefully prepared stock and will require it to be sanded down completely to bare wood. If they do it without heat, it will not blister but the flow out will not be quite as perfect. Be prepared to sand between coats and use a good water based sanding sealer before you turn it over to the body shop in order to fill the grain and reduce the number of finish coats required. Oil based sealers will amber.
 
I have had problems with the automotive finishes chipping could be my application, it was for a bench rest rifle, it had an impact on the edge of the end cap and a quarter sized chip came off. Also had it peal up at the butt on another one.

As to RayfromTX concern about heat causing water vapor and causing blisters I have heard that as well, but I was told their were new finishes that use ultra violet light to harden the finish, this would take care of that problem.

I have always used a product from Cgnat with great success no yellowing but expensive. $30.00 dollars a pint but it takes 2 ounces to do a stock.
 
two words water separator use one on your air line as well as an in-line filter to keep contaminates out of your finish
 
"flop control" was the term my auto body guy used when he dulled the shine off my B-R-I-G-H-T yellow AR. It was disposibe furniture and for a gag, sure got some responses :eek::D
 
Spray can....

I went to the auto paint store to see what quantities I had to buy to clear coat a stock (i.e. how much was it going to cost me), and the counter guy brought out a large spray can of clearcoat! It was less than 10 bucks and made by PPG for flashing in repairs. It was more than enough to do the stock and did a good job.

Jim
 
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