Trouble with varnishing... - PeachParts Mercedes-Benz Forum

MercFan · #1 01-08-2010, 04:30 PM

I've been working on re-finishing my shifter column as it was very worn out and cracked. I stripped the old veneer and re-glued new Zebrano, followed by nice Sedona Red stain - was looking good and smooth so after drying I've started planning the last finishing steps.... that's where my troubles started...

I first purchased the bar pour but after reading the instructions I returened it back to ACE and got a spray can of McCloskey's Spar Varnish - it's for marine use, UV protection and tolerates expansion/contraction of wood... .so it looked promising.

Trouble is that when I spray it and I let it dry under a cardboard box I get a small portion of it looking good and smooth but large swaths of it have tiny little wrinkles all over the finish - too much spray maybe?! Don't know... I've tried little spray and lot of spray, I can't seem to get it to look right... I have about 20 coats on it now and it still looks like cr&p...

Looking for some options - perhaps I should just buy a can of stripper and remove all of the varnish and start over?! Or just buy the bar pour again and coat a thin layer over the top of it!?

Any advice will be welcome...

Thanks,
James

Mike D · #2 01-10-2010, 07:41 AM

The little wrinkles are probably a form of "solvent pop". It occurs when the varnish reacts with a chemical, solvent cleaner or most likely the stain you used. Remove the varnish, clean the surface with de-natured alcohol, let dry EXTREMELY well and try again. If the problem re-occurs then you are going to have to use the "brush on" spar varnish. I don't think the Bar Pour will hold up to the sun's UV rays.

MercFan · #3 01-11-2010, 10:58 PM

Quote:

Originally Posted by Mike D

The little wrinkles are probably a form of "solvent pop". It occurs when the varnish reacts with a chemical, solvent cleaner or most likely the stain you used. Remove the varnish, clean the surface with de-natured alcohol, let dry EXTREMELY well and try again. If the problem re-occurs then you are going to have to use the "brush on" spar varnish. I don't think the Bar Pour will hold up to the sun's UV rays.

Thanks for the advice - I've had good success with stripping the old varnish and re-staining it... waiting for it to dry out then I'll try the Spar Urethane tomorrow (high gloss)...

jmk · #4 01-13-2010, 09:16 PM

This is one of the difficulties with finishing wood--air entrapment.

The problem is not with the chemical nature of the varnish (though admitedly popping severity is formula related), it is the nature of wood. Wood is very porous and when a varnish is applied, trapped air in the wood comes out a pops the finish.

The best way of correcting this is to apply a thin coat with a high quality brush. Alow to dry overnight. Wet sand with 300-400 grit paper. Apply with a brush. Wet sand. Put on at least 6 coats of varnish or until you get the desired appearance. This is the technique for refinishing wood to get a perfect finish.

Look up "brightwork" on Amazon or at your library and you will get yachtsman's tips for getting the desired high quality look.

I never did work with Mercedes on their wood coating, though I always wondered how they got such a good, consistent finish over wood. I suspect they had special applicating machinery and coating designed to run in the equipment.

Varishing wood is not trivial. The father of the guy who taught me how to do brightwork was one of the world's best at this. My skill level pales in comparison to both of them.

You will get better results with the spar varnish if it is actually a phenolic varnish than with a urethane. Urethane is much harder to wet sand.

compress ignite · #5 01-13-2010, 10:45 PM

http://www.woodweb.com/knowledge_base/Avoiding_Bubbles_with_Spar_Varnish.html

I particularly like these three Varnish Technique Advisors:

posted 08-11-2004 10:35 AM ET (US) Profile for PeteB88 Send Email to PeteB88 Use the real thing - - ZSPAR, Epiphanes etc. Do the prep right, take some time, make sure you use the best possible sandpaper, "sanding between coats" is NO BIG DEAL, it is only scuff sanding to create a mechanical bond for the next coat. I got the whole program down, have done it dozens of times. In my experience, doing it right with excellent marine grade finishes, you do not need to do a gazillion coats for a great finish. It's a boat, not a piano. REMEMBER - -the single best indicator for time to recoat is when the finish loses 50% of its gloss. All you do is scrub the gunk off the finish, scuff sand and coat, - - usually two will do it for another 3-5 or more years. Use high gloss, Captain.
OutrageMan posted 08-11-2004 01:34 PM ET (US) Profile for OutrageMan Send Email to OutrageMan Spend the money and buy real spar varnish. The name in the can is just marketing hype. It is still a urethane, and not a flexible as a spar varnish.

I try to remember this quote:

"There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey." John Ruskin

Here is the latest response from MinWax - I asked them about using Helmsman on a boat in a marine environment:

"Thank you for your inquiry. The Helmsman Spar Urethane can be used on exterior wood surfaces, however a couple things to keep in mind:

1. The product is a maintenance coating. It should be recoated every 9-18 months based on weathering. Consistent water contact may require a touch-up every 6-9 months.
2. It should not be used in any area that will be submerged in water.

Sincerely, Keith"

from this website:
http://continuouswave.com/ubb/Forum3/HTML/006866.html

and:
http://continuouswave.com/ubb/Forum3/HTML/009779.html

jmk · #6 01-14-2010, 02:00 PM

Good advice. 3 coats with wet sanding should do it. Just make sure you sand any air bubbles out. This will be primarily with the first coat. If you go to 6 sanded coats you will be amazed of the finish quality.

Another coating I would recommend is Pratt and Lambert Vitralite R7 UVa spar varnish. It is an extremely good coating. I would not use any of the Minwax products. True phenolics work better over wood than urethanes.

One word of caution with phenolics. Run a test to see if you like the color. You can make a urethane water white. A phenolic will always have some color. The P and L product is a little darker than most because of the UV absorber used in it. Test on a scrap piece. Personally I find the color from the phenolics to be better than water white, but that is a preference of mine, not yours.

jmk · #7 01-18-2010, 02:24 PM

Oh yea, one correction from two posts ago. The sanding is really not for adhesion. Wet sanding will not significantly increase adhesion. The wet sanding is to get the desired appearance. It is amazing how that helps.

He is quite correct in that is not a big deal. I wet sanded every window in my front hall. The dash pieces you are working are rather flat and will be easy to sand.

Do be afraid to be aggressive, esp. with the first coat. The paper is quite fine and you are looking to create a very smooth surface that will enhance the appearance of the next coat and dramatically decrease the sanding of subsequent coats.

StaggerLee · #8 06-20-2010, 03:03 PM

When doing brightwork on raw wood, I always thin the first coat of spar varnish. The wood absorbs the thinner easier and it pulls varnish in to the pores of the wood to help seal it. I use 150-200 grit between coats and 4-600 before the final coat.
In my experience, wrinkling comes from too thick of a coat - A skin forms on the thick areas and as the deeper paint hardens, it shrinks the skin causing wrinkles. (Kind of like getting in to a cold swimming pool)

jmk · #9 06-21-2010, 05:58 PM

That mostly makes sense to me. Adding mineral spirits will reduce popping (air entrapment) and will cut down on the sanding.

Maybe I'm just a masoshist for sanding, but I would never get away with using 150 grit on a varnish. I would end up taking too much finish away. 400 grit is a lot safer, and the water helps lubricate and cool the phenolic. It takes a while for them to develop full properties, especially the mechanical properties.

Wrinkling can be from too thick of a film, but there are two other common causes: putting on the next coat too soon or having too much air circulation while the coating is drying.

If you place the next coat on before the previous is dry enough, the solvent from the freshly applied varnish can actually attack the previous coat.

If there is too much air circulation, you can have the top layer of this coat drying so much faster than the bottom that the dried part sinks into the still wet part. This creates a wrinkled surface. The same basic mechanism as too thick of a coating, though with a different cause.

Stretch · #10 06-22-2010, 01:09 PM

This might sound daft - but I saw it once on Discovery Channel so may be there is some value in it! On one episode of Orange County Choppers they were varnishing some furniture for the big boss and finishing it off with a blow torch to remove bubbles... I've never tried this and I'm not sure if this is a good source of information - so take this suggestion with a large pinch of salt.

lorainfurniture · #11 06-22-2010, 01:36 PM

Is it wrinkling in the same spot every time?

If so, there is something on the wood.

If it is wrinkling in random spots, you might be applying coats too soon, or any of the above

I used bar pour on on my shifter console, and it took MONTHS to finally harden, and it still scratches easily.

It seems mb somehow managed to pour plastic on their wood. That stuff is a pain to get off.

TX76513 · #12 06-22-2010, 03:31 PM

In a past refinishing thread it was mentioned the user copied MB's supplier using "Clear Cast" a 2 part Acrylic Resin.