We built a door from Black Walnut last year, 2019, for a home. The door was installed in September. We provided the door finished with Epifanes Rapid Coat product (Marine Grade Varnish).

In the beginning of June 2020, the homeowner discovered the finish bubbling. Please see pictures. The finisher put approximately 6 - 7 coats on this door.

Has anyone using Epifanes or other exterior grade finishes experienced this?

Anyone thoughts on why this is happening and what would be an appropriate way to fix the issue?

Any other suggestions for exterior grade finishes for these applications?

Thanks, Chad

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Hi Chad,
We use D-Dur ( by Chemcraft) for clear coating in well protected areas. Is this only happening on the exterior side? Is it bubbling below all the clear coats or is it separating between layers of the varnish?
Is the inside finished with the same product?
Without knowing anything about this situation and not using the same finish product are, My first guess be.
Moister trying to escape from the interior of the building or the wood itself. perhaps from glue in the mortice and tenon joints?
Looks like the attached pictures are close to joints.

I dont know a lot about building exterior doors but the pictures look to me to be at the base and seeing what looks to be a a simple panel raise and cope and stick cant help but to wonder if water is pouring in those raised panels at the base, being sucked in, and trying to get out.

That image showing the panel raise in the sticking looks like a nightmare to me.

It might help to offer details of construction and finish prep.
I don't think this is a moisture issue. It appears that the construction method is walnut skins on a core. The bubbles appear to be in locations where the walnut grain is showing end grain like pores. Is it possible that these are areas where lamination glue bled to the surface? The finish may not adhere to the glue saturated wood in those locations. Other areas of lift are in the corners at the base of the side lights - also an area where excess glue could lie on the surface.

Almost looks like something was spilled on the stone or some cleaning chemical? Haze on the sidelight bases and also a random spill look on that stone threshold by the door. Almost looks like bleach on the stone. Going to be hard to prove, but that pattern on the threshold looks like strong evidence to me!

The doors are made from pattern grade mahogany. Stile & rail construction. We build our stave core with edge bands and then glue the veneers(skins) onto the core. I don't believe that glue is seeping through the veneer as we don't apply more than needed when making our stiles and rails.

There are no bubbles on the end grain with the exception on the bottom of the sidelight.

I don't believe anything was spilled onto the stone sill or the door as I put my hand over it to feel it. It did not have a different texture and seemed to be part of the characteristics of the stone.

We did notice that the bubbles only occur halfway up the door. Which leads me to think that it may be an issue with the sun hitting the door in the late afternoon. Would still think a marine grade varnish would be able to handle that.

Hi Chad,
We do see problems due to sun and heat in the Canadian Rockies. I have never seen it
in the form of bubbles. It mostly happens due to wood movement below the finish, like separation of joints or glue line failure due to heat.

Thanks for your comments Fred -

You would think that if there was going to be movement, it would occur where the stiles and the rails meet or movement in the panel (expanding & contracting). The bubbles are showing up in the middle of the parts (stiles & rails).

What product do you use for finishing an exterior wood door?

Chad

Hi Chad,
For exterior clear coats we use a product by Chemcraft called D-Dur. I is a older product we have used it for quite some time.
The good part about it is it has a fair bit of flex, that can be helpful. The bad part is the slow curing time.

We use Sikkens Cetol for our exterior finishes, almost without exception. We have never had a problem like what you have. We prefer it because when the finish is aged or faded, it is easy to recoat. If for any reason the finish has to be removed, it is relatively easy compared to the epoxy finishes and others.

Like Rich, I also think it is something spilled on the wood, also spilled on the stone. Water will raise the grain and you will feel it, but bleach, acid, and many liquids will not raise grain, but will repel the adhesion of the finish. I think it so obvious as to hardly question if it could be anything else (though you are right to investigate - one never knows.)

Was the work finished on site, or in your shop?

Chad:

I also do not build many exterior doors, for precisely this reason.

Nonetheless, I agree with Rich C. that something was spilled onto the stone threshold, and it looks like it may have gotten onto the door. It appears that the staining is mostly on the threshold at the active door leaf, and it also looks like something was spilled and then something else was used in attempt to clean it.

If that is a block nailed to the porch deck that is securing the right end of the door threshold with the shim, I would wonder if something like muriatic acid was used towards the end of mortar cleanup, and some splashed onto the door. The liquid trails run down onto the sub-step, and it appears that some attempt was made to wipe it off of the horizontal surfaces of the millwork at the sidelights, but perhaps no attempts to wipe the splashing on the vertical surfaces.

Or perhaps a cleaning agent was used to try to clean up whatever the brown staining is on the active leaf threshold. The pattern of finish "defect" looks more like a spill or splash, rather than something occurring because of the exposure of the finish to the weather.

At least that is what it looks like to me.
TonyF

Crazy things happen but there looked to be a blister at the mid rail on the hinge stile of the right door and its pretty high up and all by itself and they all looked to me to be right at the joinery which seemed interesting. Of course any cleaning could have splashed/gotten anywhere.

I wonder how deep the blisters go into the finish- between coats or to the sealer used or even under the sealer
It looks to me like its contamination during the finishing process.

Since many people are convinced something was splashed onto the stone sill I called the homeowner. He sent me a picture of the door after it was installed. He confirmed that the stone sill had those characteristics in it and something did not spilled onto the stone sill. You can see it, if you zoom in on the picture. Chad

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Can you get someone (preferably chemical technician) from Epifanes to look at it and give their opinion?
A-

There is one thing for sure, blisters aside, your photos are far nicer than that one and its a stunningly beautiful door. The more you look at it the nicer it is.

I would have guessed moisture for sure but the blister on the right stile right door is odd. But there is a lot of character and visible voids that look great though you'd wonder what moisture/water they would allow in or allow to wick up.

Guesses only.

x2 for Sikkens Cetol. I stripped and refinished with Cetol (forget the color) on three sets of French Doors, less that a mile from the ocean. Six years later, they look like the day I did them.

The image that made me think of a spill was the close up in the 2nd picture of the original post. If that isn't a spill, what is the smeared look on the horizontal board next to the stone? And why is it heavier in the corners. It's completely different than the blisters.

I saw that as dust

The Epifanes representative claims that it is due to extreme heat.

Chad

Well, Chad did he say not to use their product somewhere that gets hot?

I have seen this in a Western exposure door painted dark green. My assessment, and I'm no chemist, was that the heat caused the air within the door to expand. Most finishes I think will or should allow the air to escape, but I wondered if some of the new formulations may be too impermeable, and the pressure inside was greater than the adhesion between coats.

The paint and bubbles I'm talking about were still very flexible even after several years, and were the top SWP formula. Yes we all want a finish that can expand and contract with the changing moisture content in our exterior doors, but maybe there needs to be a bit less elasticity, or better adhesion between coats.

Maybe better sanding between coats, giving more tooth for the following coats would prevent this. But probably most of the sanding is done after the sealer, who sands between the final coats? Maybe there was a short window of opportunity for cross linking that closed from waiting too long due to rain or weekend.

I will bet lunch that the bubbles are not from heat. Try using an infra-red thermometer on it when the sun is 90 degrees from the face, and clear sky. I say you don't get over 180 if that. What does Epiphanes say is the maximum heat?

If moisture from outside, then the sidelight bottom rail cut at the sill would blister all the way across. It is not moisture migrating up thru - too perfect of a drip.

If you finished in your shop, then quiz everyone. You may need to use electricity, but I bet someone will fess up. Those drops are too perfect, and no reason for being where they are, other than random. It just might be Mountain Dew.

Same if it was finished on site, you just have a larger pool to interrogate.

If you can peel one of those blisters, that may tell you whether the bubble is on top of the stain, or in one of the topcoats. It looks like it may be dripped contamination between topcoats. Possibly sweat?

Hi Chad,

We did have occasional contamination from silicon, oil or just dust. It was always visible and reacting within a few days not months. But we never use varnish.

I may be wrong, but I thought with silicone contamination, the finish would contract off / fish-eye while the varnish was still wet.

The only way that was caused by heat is with a torch.

Epifanes is one of the best varnishes in the world. It’s on millions of boats sitting in full sun that would hit 120F.

If it was a heat problem, it would not be so isolated. I believe it is either a contamination issue below or above. Heat may have made it worse, but it is not the cause.

If there was enough heat to cause finish bubbling then there would be structural changes in your joinery.

We see heat problems on door that are painted black with full sun.

Beautiful doors by the way.

Chad - Have you peeled off one of those blisters yet?

How is is it shaking out - will you just refinish in place?

Lots of questions....

Would it cost less to make some temporary doors to secure the opening while you took the doors back to the shop to refinish in a controlled environment.

I would talk to an independent lab and see if they could analyze something off the surface to determine cause.

I think at this point determining the cause if they can't scrap something off the surface and test would be more expensive than repairs. A simple test might be 2-5k .

Your insurance might pay for the test.

That looks like a common problem we see on exterior finishes and epoxies. We do a lot of exterior work including boats. Our finishes haven't had any problems since we started using Smith's Multiwoodprime before top coating. Some of the topcoats we have used on boats are Epifanes, Bristol and Awlgrip including pigmented products. On furniture using SW nitrocellulose lacquers, conversion varnish and 2 part polyurethanes. I've used it on exterior home repairs under latex paints with no problem.

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