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-   -   Urethane On Wood (http://www.hotrodders.com/forum/urethane-wood-55618.html)

jcclark 01-07-2005 07:41 AM

Urethane On Wood
 
I have always sprayed furniture lacquer on cabinets
and heve read lately on other forums that some guys
are spraying auto clear urethane on wood.
Does anybody know about this? Can I use my "car" clear
on wood? I have a lacquer sealer I put on first then scuff
before topcoating. Would this be a acceptable base
for the clear? My stain is an oil base so I don't think
I would try the clear over just that.
Any input is greatly appreciated.

willys36@aol.com 01-07-2005 07:45 AM

This topic was just discussed in a thread within the past week. In answer to your question, in general, yes, urethane clear goes over wood well. Specifically, I suggest you try your formula on some test pieces to see if all the products are compatible.

Bluepen 01-07-2005 09:27 AM

In '03 on one of the Hot Rod shows on TV, I think it was Street Rodder or something, they had a Street Rod of the year contest and they had a custom woodie on it and they used clearcoat on the outside exposed wood and it looked real good.
I know I'm planning on making running boards for my '46 Chevy Panel from Oak but not sure of the finish yet, I was thinking of some kind of a marine finish might be better.

David

jcclark 01-07-2005 10:39 AM

Willys
 
I also thought about making the samples but unlike cars,
furniture is built for a lifetime and I'm not convinced that
good adhesion for the next year or two means good for
the next 50 or 75 yrs. My furniture will last longer than that.
I did spray car lacquer once and it peeled off like a plastic
sheet. Apparently furniture lacquer has something in it
different that lets it stick to wood that has been stained.
I don't think "unstained" wood would be a problem .
I guess my question is would "stained wood" with furniture lacquer sealer,or furniture lacquer (topcoat) be a compatible base for urethane? I've heard some urethanes can go over lacquer,
But they were talking about automotive lacquer, and that's
different. I may need a company tech rep for this one.
But thanks for yours and everyones input.

willys36@aol.com 01-07-2005 10:51 AM

My guess is that your only concern will be infant mortality; if it cures over your sub-coats and still looks good and is still stuck after a week or so, it should last forever.

daimon1054 01-07-2005 11:34 AM

Would you want to add a flex agent? Wood expands and contracts and I would worry about it cracking or hazing. I know it will go on and stick but how long will it look good? Wood working urethane is flexable to some extent.

oldred 01-07-2005 12:11 PM

For what it is worth, I use Nason clear coat on walnut gun stocks and have never had any problems. My Marlin deer rifle has been wet a number of times and so far it is holding up just fine. Also years ago I used auto lacquer on UNstained walnut wood with no problems.

antiquecar 01-10-2005 06:13 PM

I am sure that most people are talking about a clear coat but i last year painted the roof on my 23 Dodge Screenside with a catalysed primer and imron. The room has both metal brackets and a wood frame. I have had no problem so far

BarryK 01-10-2005 07:15 PM

Re: Willys
 
Quote:

Originally posted by jcclark
I also thought about making the samples but unlike cars,
furniture is built for a lifetime and I'm not convinced that
good adhesion for the next year or two means good for
the next 50 or 75 yrs. My furniture will last longer than that.
I did spray car lacquer once and it peeled off like a plastic
sheet. Apparently furniture lacquer has something in it
different that lets it stick to wood that has been stained.
I don't think "unstained" wood would be a problem .
I guess my question is would "stained wood" with furniture lacquer sealer,or furniture lacquer (topcoat) be a compatible base for urethane? I've heard some urethanes can go over lacquer,
But they were talking about automotive lacquer, and that's
different. I may need a company tech rep for this one.
But thanks for yours and everyones input.

*******************************************
As carefully as I can!
Sorry there is no difference between lacquer for furniture or for car, "except for price" Because the distributor selling that furniture lacquer is not going to tell you who is making it for them and their label.
Furniture does not have to worry about parking lot dings, UV's, or 25 cent car washes blowing the clear off, so even urethane over lacquer is not an issue for long term as it would be on a car.
The furniture industry as a whole is where the auto painters were in 1985-89 slowly moving to waterborne and urethanes and some UV coatings.

BackwoodsBum 01-10-2005 11:06 PM

One thing you need to consider is moisture getting between the wood and the clear and causing it to peel.

My dad and I sprayed the wood in the bed of my '36 with clear Imron the first time we built it and it looked great for a couple of years, then we started to notice cloudy patches that turned into bubbles and eventually the clear started peeling off in places. It's been a long time and I've killed off a lot of brain cells since then, but I want to think it was only 4 or 5 years before we started seeing the clear peel. I've seen other trucks with similar problems whether they used urethane, lacqure, or whatever. My truck was droven almost daily and even though it was kept in a garage it was exposed to a lot of weather so if you are building a show vehicle that will be treated easier you'll probably have better results than I did.

My father-in-law (who builds and refinishes furniture as a hobby) suggested that we either had parts of the wood that were left exposed (such as the ends of the boards or the bolt holes) or the finish got scratched and the wood was able to absorb moisture (from rain, car washes, or just humidity in the air). Then when the sun hit it and the moisture started to evaporate it bubbled up under the finish as it tried to escape into the atmosphere. I don't know if this is right or not, but it sounds better than anything I can come up with so this time around I am going to take care to get a good even finish on every part of the wood before I install it. Either that or I'll just go with an oil finish which will look great but be a lot more work to keep looking good..

willys36@aol.com 01-10-2005 11:16 PM

Good point. I wouldn't clear coat any wood that is exposed to moisture. Almost impossible to keep from peeling like you described.

jcclark 01-11-2005 09:13 AM

As I said before, there is a difference between auto lacquer and
furniture lacquer, it even smells different. The auto lacquer
just doesn't stick to wood that has an oil base stain, I can peel
it off in large sheets. Won't try that again.
I don't know what's different but believe me from my experience
it's different.

BackwoodsBum 01-11-2005 09:26 AM

In the case of my 36, my sister's 34, and quite a few other trucks I know of, the beds were coated with lacquer or urethane over bare wood, not stained wood. I've described te results above. The beds were made of different typws of wood, mine was sassafras, my sisters was walnut, one friends was cedar, one was cherry, one was chestnut lumber from an old barn, and the rest were oak.

It stands to reason that any automotive clear would not adhere well to an oil based product, but in our cases the automotive finishes failed on bare wood.

The more I think about it the more I believe that the only way to get a durable and long lasting finish is to have a finishe that penetrates in the wood yet still allows it to breathe, like linseed oil, tung oil, etc. I'm definitely going to have to look into this much more before I finish my truck this time.

pmeisel 01-11-2005 03:57 PM

Another Way - www.westsystem.com
 
The real hot shot marine guys 'round here (I'm not one of them, I just have talented friends) use West System Epoxy -- one of their products is designed for clear coating. (207 Hardener).

Read the literature to confirm for your application, but if you can use it on a boat the moisture and UV a car sees shouldn't be a problem. For constant exposure to UV it may need varnish on top of it. But -- properly applied this stuff is impervious to moisture.

willys36@aol.com 01-11-2005 04:56 PM

Re: Another Way - www.westsystem.com
 
Quote:

Originally posted by pmeisel
The real hot shot marine guys 'round here (I'm not one of them, I just have talented friends) use West System Epoxy -- one of their products is designed for clear coating. (207 Hardener).

Read the literature to confirm for your application, but if you can use it on a boat the moisture and UV a car sees shouldn't be a problem. For constant exposure to UV it may need varnish on top of it. But -- properly applied this stuff is impervious to moisture.

Problem comes from moisture from the bottom of the planks, scratches, etc. Marine guys coat their wood with fiberglas cloth inside and out, then clear epoxy and/or marine varnish. Still, if not continuously maintained, water gets into the wood and starts to separate the top coating. Best finish for a truck that isn't a trailer queen is a penetrating oil.


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