Finish Frustrations

[LP]

It's been a season of failed coatings. I purchased an air sprayer this season in the hopes of getting professional quality spray finishes on my boats. I figured there would be some learning curve on the use of an air sprayer, but I am finding out it may take a little more than a little bit of trial-and-error to get a quality finish. Three coats/tries and almost a quart of Petit's 2015 Flagship Vanish on one side of my 16' sailboat and I still only have a marginally acceptable, slightly orange-peeled finish.

My first try, I thinned the vanish slightly had fairly acceptable results, except that I had some "dry" areas that I had missed getting good coverage on.

The second attempt, I thinned the varnish a little more and got better flow, but also got quite a few runs and sags, but good glossy finish otherwise.

With the final coat, I used less thinner and ended up with the orange peel as stated before.

Confessions first. I used the TLAR method for thinning and just used off the shelf paint thinner. I see two problems with my current attempts. A lack of a method for consistently thinning the product to proper vicosity and the use of a possibly substandard thinning agent.

I am curious as to methods employed for measuring quantities of varnish and thinner. My paint bucket has no graduations so it is best guess as to how much product I'm actually starting with. I guess I'm asking the most efficient way measure out product without having an excessive amount of measuring devices to clean up afterwards.

Am I hurting the product by using paint thinner? Reading the 1015 (as opposed to 2015) can last night, there were two recommended thinning products for brush application based on temperature and a third type for spraying. Can the thinning agent make that much difference? As a home builder, I'm somewhat reluctant to purchase a plethora of product that is going sit on my shelf for ten years before the unused portion gets thrown away. On the otherhand, I suppose the thinning agent has an almost indefinte shelf life and may still be servicable after all of those years. I guess the $100 question is, "Does using the manufacturer recommended thinning agent make enough difference in product performance to warrent using it?"

An unanticipated effect of air spraying was the incredible amount of overspray associated with the method. My entire shop was a fog by the time I had finshed spraying! I would venture to guess that half of the sprayed product stayed airborne and settled on shop surfaces. I had masked, but not to the extent that was required to protect all of the finished items in my shop. Is this also typical? Is this an indication of an air setting being too high?

After my woeful attempts at spray coatings, I decided to fall back on brush coating my current runabout project (See photos) as my brush technique surpasses my spray technique right now. I've always had had great results with Petit's 1015 and brush coating. This time, I just couldn't keep a wetted edge going. Argh!!! I'm thinking I did my other brush coats at a lower temperature. This last attempt, it was around 80 degrees in the shop. I'm wondering I little thinning would have been in order. I'm hessitant to thin though because I'm getting some sanding marks telegraphing though the finish already. This is a bit confusing as I had wet sanded with 320 grit sandpaper in preparation for the final coat.

This is all very frustrating as I have been working this project for TOO long. I am so close to finishing, I can taste it! I'm currently resanding the forward deck and will hit it with 320-400 grit in an orbital sander before trying another coat of varnish. I've have lots of shiny new hardware that is just itching to be installed as soon as I can get a final coating that is worthy of the project.

All input is appreciated. Thanks!

[BHOFM]

The best method I have found to get accurate repeatable results is
to use a straight sided can and measure with a metal ruler.

For one part in ten, just measure nine inches of finish and one inch of
thinner.

Or four and a half inches of finish and half inch of thinner.

Just adjust to the ratio and amount you need.

The metal ruler cleans quickly and the results can be repeated
any time.


The old metal coffee cans worked well, or you can buy cans at
an auto refinish supply house.


http://img60.imageshack.us/img60/7707/dscf1355.jpg

[mastcolin]

1) the thinner makes massive difference to performance of material. A spray thinner is usually faster evaporating than brush thinner. A hot weather brush thinner is slower evaporating than "standard". You can sometimes get away with your own thinners but why take the risk? To repaint is more expensive than the thinner no? ps one pack alkyd varnishes are invariably white spirit thinned to brush.

2) your air sprayer is possibly very inefficient/too big an opening. You will perhaps struggle to get decent finish whatever you do.

3) a conventional spray gun is estimated to be about 50% transfer efficient. ie for every litre you spray, 500ml will not end up on the target. Your talk of fog doesn't surprise me.

4) sand scratch marks can come from variety of reasons. Firstly you say 360grit, but what type of paper? Proper wet and dry (the black paper) at 600 grit is approx equivalent to 400 grit 255 gold grade paper from 3M. Every brand of paper is slightly different. 3M p360 255 grade paper should be ok, anything less is too rough in my estimation
5)If were having runs, you perhaps sprayed too thin/wet. This will look ok wet but when it dries solvent evaporates and it may show scratches. The wetter you spray ie too close gun to surface, the less solvent will evaporate in transit between gun and surface and the varnish will shrink more on drying (and run more!). The better guns generally produce more atomising air so drive off more solvent and deliver more solid material on surface.

Best of luck!

[cudashark]

Dear LP,

Stop using Varnish. I use Dupont Imron MS1 Poly. It sprays on at 3 coats at a time. Dry overnight and sand with 400-600 grit. Spray on 3 more coats. Let cure a week and wet sand then buff just like a car clear coat. MS1 has the highest UV protection and Solids in the industry. If scratched treat as you would a car finish. Sand, spray wet sand buff. No problem.

See my pictures in the "gallery" section under "Cudashark"

Ray


http://www.boatdesign.net/gallery/showphoto.php/photo/14594




http://www.boatdesign.net/gallery/showphoto.php/photo/14594

[hazegry]

you might be having trouble with the finish but the boat looks great I like the accent color could you post more pics of it when you get a chance thanks.

[alan white]

I think the advice to go with poly is probably right. Traditional varnish is very sensitive stuff. It goes down well only under a very narrow set of conditions. Modern formulas are a snap in comparison. i've noticed that when I became proficient at brushing varnish, brushing any kind of paint perfectly became child's play. Varnishing is practically an art and spraying it would be no exception.
So as long as you're spraying, use a polyurethane and you'll have much more control.

[gonzo]

Use a viscosimeter you can buy it at the paint store

[rwatson]

hahahahahahahahahahahaha - the man is building a dining table to take out in the sun, sand, rocks, mud and scratchy zippers of lifejackets.

Nothing against great finishes ( and thanks to all the great contributions here) but whyyyyyyyyyy !!! :D

(Yeah, yeah, I am a grumpy old pessimist)

[LP]

Thanks for everyones responses.

I will have to look into the poly aspects, next project. I'm commited to varnish on this one as I only have one coat(I hope) left to do.

I was wondering if there wasn't a finish that could be wet sanded and buffed to a shine. The Imron certainly will bear some investigation.

To rwatson: fame. I get my 15 minutes everytime I go to the lake, 15 seconds at a time. :D :D :D

[cudashark]

Dear LP,

You can wet sand and buff varnish when its fully cured. Buff at a slower speed than poly.

The biggest problem with wet sanding and buffing varnish is that the hardeners and UV protectants migrate to the surface of the film as it dries. So you will be removing these aspects of your last coat.

Ray

[gonzo]

One of your problems is that you expect a professional finish from your equipment and lack of training. What you are getting is typical for a begginer. Even professionals sometimes get runs and other problems.

[PAR]

I'm buffing out a number of sags this weekend. Get over it and move on.

[rwatson]

OR you could invest a lot of money in THIS

http://www.akzonobel.com/news/pressreleases/2009/akzonobel_launches_energy_efficient_led_spray_gun.aspx

a spray gun that cures as it sprays.

Sounds wonderfull

[LP]

Hey Paul,

sssssppppppplllllllllltttttttt!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

:P :P :P :P :P


But seriously, I've never managed a good buff job on vanish. Is it possible? Details?

[PAR]

Yea, you can do it, but you have to be careful and make sure the varnish is cured, not just dry. It takes over a month for it to fully cure.

I'm buffing clear coat LPU, not varnish, which is easier and more durable too. I've been using this as a top coat lately to offer more protection and durability.