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Microbubble mess in my varnish

Posted by caneyqueen 
Microbubble mess in my varnish
April 03, 2018 03:37PM
Have applied 3 coats of Epiphanes Wood Finish Gloss per below and have thousands of microbubbles. thought I'd avoid lots of sanding and go with this product that can be recoated without sanding within 72 hrs and has rave reviews on Jamestown Dist, amazon, etc. ended up with a big mess.

1) coat 1 applied with china brush over west system cured for at least 6 months, sanded 220 and vacuumed/wiped with denatured alcohol rags
2) 24 hrs later lots of microbubbles that I thought were dust so sanded to 320 wiped with tack cloth as was worried about denatured alcohol potentially causing issues and recoated with brush again
3) 24 hrs later enormous number of bubbles (see attached photo) so sanded to 320 again, vacuumed and waited additional 24 hrs for dust to settle and wiped with denatured alcohol rags again and recoated with brush and immediately covered with new plastic dropcloth suspended 12 inches above surface and vented on both ends of boat.

been 2 days since last coat and I have the mess you see in the spotlighted area of the attached photo completely covering all surfaces varnished. I've spent over 300 hrs on this custom west system/marine plywood driftboat and used mahogany and tiger maple so brightwork would be stunning but now have a mess. shop temp was consistent 70 degrees using heaters.

what do you think is going on and how do I fix...?

Re: Microbubble mess in my varnish
April 03, 2018 04:38PM
That's way worse than usual, which I cannot explain.

However. All fiberglass skins breath a little. Enclosed standing platforms people sometimes build into the front end of a fishing boat will eventually fill with water, not because they leak water but because they leak air, gasses. vapor, that has dissolved water vapor which eventually condenses.

To apply a finish coat on top of any glass over plywood it's important to get the shop very warm, for at least an hour. Then back off on the heat a bit, so there is a warm but steady or even slightly falling temperature as you apply the finish. That minimizes the tendency for gas to bubble up out of the underlying panel. Problems like this are worse in cold wet weather. In dry areas like Montana we have less water vapor in the air and therefore less moisture lurking in the underlying plywood.

What you show is extreme. It's possible an additional finish coat of resin--prior to paint--might have been a good idea.

But I would not even think about removing anything now. You can work with this. Sand it out lightly. Heat the shop to July temperatures. Back off on the heat. Paint again.
Re: Microbubble mess in my varnish
April 03, 2018 10:25PM
there's at least 3 coats of west system on the panel already...epifanes tech support swears it's dust but I had last coat completely covered with new plastic dropcloth about 12 inches above finished surface immediately after applying varnish. ends of the dropcloth were open so varnish could cure... so dust would have had to travel straight horizontally into both open ends of plastic dropcloth 6-7 ft and then drop onto finish evenly across the 10 ft deck as whatever it is distributes pretty evenly across the whole panel. with no air movement whatsoever in garage I just don't see dust moving like that. I've sprayed pieces in same garage with 4 stage apollo hvlp system with virtually no dust issues so I think they're wrong. I took pics with 12 megapixel camera zoomed as close as it would focus...attached. dust or bubble...I don't know.
I also tipped/rolled alkyd enamel onto outer hull with boat inverted in same garage few months ago and had minimal dust issues.

Re: Microbubble mess in my varnish
April 04, 2018 01:10AM
What I said earlier about gas bubbling up from the plywood does not apply here. I do not know how to explain this.

I have an HVLP system. I've not seen anything like that. But when I use it I always use automotive paint. I've never worked with Epifanes. I wish I could help but...I can't. Not in this case.

The trouble I have with automotive paint is always about spraying too much and getting drips. I've gradually learned to do lighter coats and more of them. The hard way.
Those bubbles look like...........the wrong thinner or reducer? Those are big bubbles. They look like a chemical reaction after the spray.
Re: Microbubble mess in my varnish
April 04, 2018 07:59PM
I brushed on the epifanes...reference to hvlp was just to say that I've sprayed in the same garage space on other projects without dust. epifanes rep is convinced it's dust but there's no way. I covered the horizontal surfaces with new plastic dropcloth within 12 inches of surface immediately after brushing on the varnish.

gonna take your advice and sand/recoat in hot space.
Re: Microbubble mess in my varnish
April 05, 2018 11:08AM
When you sand that out the bubbles will leave micro-thin craters in the finish that is there. You might want to touch those with a small artists brush to fill the micro-crater.

Let that dry. Sand lightly again. Now go over top with a real coat. Might try some finish on a test panel first too, before that next real coat.
Re: Microbubble mess in my varnish
April 06, 2018 09:19PM
The posted picture shows clear blobs...looks like bubbles....hard to be sure in the view.

I've never seen anything like that before. As Sandy suggests, it might be a reaction of the varnish with the thinner, or with the alcohol used to wipe down the dust. Try wiping with the brushing thinner or mineral spirits.

Since you brushed on the varnish, it might also be varnish that dried in the brush that wasn't cleaned out thoroughly. Hardened varnish that sheds into the new coat might look like bubbles since it will be the same color as the varnish coat. I use foam brushes for varnish since I like to avoid the solvents needed to clean bristle brushes.

Using a new brush I would coat untreated scrap pieces and see if the native varnish produces a similar result.
Re: Microbubble mess in my varnish
April 09, 2018 05:36PM
Appreciate the comment Eric. I used a new brush and left it suspended in thinner between coats, shaking it out before each new coat. I didn't thin any of the coats as application was over cured west system epoxy vs raw wood so didn't think thinning was necessary as there would be no varnish soaking into/penetrating wood fibers. If thinning might help eliminate bubbles I'm ready to try that.

The Epifanes product I'm using (Wood finish gloss) has some sort of additive in the varnish that keeps pores open for recoating within 72 hrs without sanding...it's compatible with varnish so thinking I need to switch to regular varnish and get away from original product. I'm now absolutely positive it's bubbles as I also varnished the anchor arm which isn't yet installed and covered it with a clean box immediately after application and it has same issue and same heavy coverage of bubbles as the boat.
Re: Microbubble mess in my varnish
April 09, 2018 08:11PM
I haven't use bright finish in a long time. I used to spray McKloskey's Marine Spar Varnish thinned with Penetrol.

Then I tried clear automotive finishes. Now I usually just paint but if I do want to see wood I sand it smooth and rub on some oil, when ever it starts to look a bit dull I rag on some more oil.

There are fancy semi-secret recipes for various obscure oils mixed with Japan drier (what ever that is) and other weird stuff.

I just use lunseed oil or tongue oil and paint thinner, mainly because I can buy it at the local hardware store.

Automotive paints look great right when you finish. I like the extra extra nuclear bright metalic finishes--the ones that look like they were meant for a funny car at Daytona. But it's a boat and it does get scratched up. Regular alkyd based paints are easier to deal with because you can roll them on and then brush them out, to a nifty finish (as you did with the Epifanes Headache finish). Pettit Easy Poxy (which is NOT epoxy) is a good compromise.......not cheap but not wildly expensive.

I've seen boats painted with water base house paint. Once they're 3 or 4 years old they all begin to look alike.
Re: Microbubble mess in my varnish
April 10, 2018 09:57PM
I painted sides with Kirby Alkyd Enamel and it went on great brush/tip. I just thinned the epifanes 25% with epifanes brushing thinner, sanded/coated a small area about 8x8 in and put a clean bucket over it. if that's got bubbles in the morning I'm sanding the decks and painting with Enamel to match hull.

Disappointing as hell after a year's work looking forward to a nice brightwork finish. Went out of my way to hand-pick nice straight grained african mahogany (don't think you can even buy philippine anymore?) for gunnels and tiger maple for anchor arm and other trim. See anchor arm attached photo.

Haven't used varnish before but have sprayed lots of urethanes with no problems. I originally was gonna try auto clearcoat but was afraid I'm screw it up and have a mess...who knew I'd have a mess with varnish. not real happy with the tech support guy from epifanes...he's trying to call if dust even though last coat dried under plastic dropcloth and small test 2 days ago dried under a bucket and all have the same "dust"...that's bubbles folks !

Re: Microbubble mess in my varnish
April 11, 2018 05:02AM
I use System 3 Marine Spar Varnish for gunnels, decks, and other bright finished parts of my boat.

It is a urethane varnish, levels fine in my conditions.

Good luck finding a solution that works for you.
Re: Microbubble mess in my varnish
April 12, 2018 02:00PM
got my heat gun, scrapers and sander out yesterday and took varnish off the sidedecks. gonna paint side decks with same paint as outside hull. not sure what happened with the varnish, but not gonna have a crap looking boat after hundreds of hours of work.
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