Interior finish questions - problems encountered.

[Esteban]

I'm having durability problems with my interior finish and would appreciate your ideas. Varathane water based outdoor spar urethane isn't working out well.

The Problem: When it's rubbed or pressure is applied the varnish bubbles up and/or peels off much too easily. Kind of like Saran Wrap. I don't trust that this water base Varathane spar varnish is durable enough to continue using it.

I stained the birch plywood that goes inside the cabin walls with water based Varathane stain. Let it dry. Over several more days I foam brushed on 5+ thin coats of the water based outdoor Varathane spar varnish. The varnished plywood dried quickly and was kept inside a dry garage with temps in the 50s to 70s for a few weeks before I permanently epoxied (glued) it to the (sandwich construction) frame. The birch plywood was clamped overnight to the wood wall frame for the epoxy to dry and harden. Many of the spring clamps made the varnish lift up and bubble. So now I have to carefully peel off the bubbles, sand smooth the lifted edges of varnish, re-stain the birch ply, and then try my best to blend in new coats of varnish. A PITB.

I called tech support at Rust-oleum and was told spar varnish is meant to be flexible. That may be why it lifted. He suggest I instead use an oil based finish or a floor finish which are harder and more durable. He said I can over coat the water based finish with an oil finish if I let the water based varnish dry for a week or more then scuff sand it. Good news, Rust-oleum will refund me for the cost of the spar urethane when I send them a copy of my purchase receipt.

So, teardroppers, what clear finish have you used that has worked out well over time? I need suggestions for a good finish that can be used for the galley too. I prefer to use the same finish for inside the cabin and the galley, if possible. One that sticks on well, looks good, with abrasion, weather, water, and some UV resistance.

Some progress to share too. At long last the walls are nearly ready to attach to the floor. I'm pleased how light the sandwich walls are - even with the outside already fiberglassed.

[planovet]

I used Minwax® Wood Finish™ oil-based stain and Minwax® Helmsman Spar Urethane on my cabinets. Haven't had any problems to date.

[tinksdad]

Another vote for Minwax® Helmsman Spar Urethane.

[Dean_A]

I used the Varathane Spar Varnish (Urethane), Exterior Gloss Oil-Based. I've used it everywhere and haven't had a single problem. I've used both the brush-on (with foam brushes) and the spray cans on smaller pieces. One thing that I've found helpful is to thin it out. I've found that many thin coats go on better than a couple heavy ones. I think the thin coats penetrate better. When I've tried putting in on full strength, it takes forever to dry, stays gummy and never levels out right.

[Mark McD]

Are you using an oil based stain? If it doesn't dry for a few days that can cause lifting. My suggestion would be to sand off the waterborne finish , restain the sides and use Minwax Brushing laquer to finish. Dries to scuff in 20 minutes and is buildable. I always spray it though. Typically I would use a catlyzed conversion varnish but these products are sold to end users- just shops-in most cases. But I've had great success with minwax brushing laquer.Here's a job done with Minwax brushing laquer:

[cuyeda]

I like the Zinsser Bullseye brand shellac. I would be interested in hearing comments for anyone with a comparison experience to the Hellsman product.

[Mark McD]

Cliff and Vanessa,
Shellac products work well. You can build layer upon layer quickly.Scuff sand between coats. Quick dry , scuff sand in minutes and buffable. If you really won't to get into it google "french polishing".

[b.bodemer]

Minwax® Helmsman Spar Urethane, for both inside and out.

[cuyeda]

Cliff and Vanessa,
Shellac products work well. You can build layer upon layer quickly.Scuff sand between coats. Quick dry , scuff sand in minutes and buffable. If you really won't to get into it google "french polishing".

Not trying to hijack the thread and stay within Esteban's request for help. I am familiar with the shellac, and pleased with the product. Especially matching some of the existing vintage tones for rework. Is Hellsman Spar Urethane a more durable product?

Esteban, sorry you are having this set back with your build. Looking forward to the finished build, as you have put a lot of thought into your details.

[Esteban]

No, I did not use an oil based stain. The stain and spar urethane I used are both water based Varathane brand products. I spent more for outdoor spar urethane thinking it'd be more durable with "Ultimate Protection, outstanding U. V. & weather resistance" and "Professional Results, fast drying no brush strokes" like the label says. Instead, I've gotten sub par durability results. Based on my preliminary results I don't trust that the Varathane water based spar urethane will hold up well over time.

Over several days I brushed on 5+ thin coats of spar varnish over the dried stain. I lightly sanded several times between coats. Since they're both water based and the same brand an adhesion problem is very unexpected and frustrating. It looks does good. The problem is that the varnish lifts (peels) off too easily even after weeks of dry time. When it peels off it is soft and a little rubbery. The pressure from some clamps made it bubble up. Also removing blue painters tape after several coats of varnish dried peeled varnish off too.

The birch plywood is now expoxied to the wall frames. If I tried to sand off the spar varnish it'd probably sand through the paper thin birch layer of the plywood and thus ruin the walls, months of work, and hundreds of dollars in materials.

So, I have two problems I need solutions to.

One - how to save the walls I've already built? If possible, I'd prefer to over coat them with a more durable clear finish.

Two - what clear finish product to use on the rest of the project?. I can use either an oil or a water based product. I do like (prefer) the easy clean up of using a water based one. To keep the color consistent I want to continue using the same stain.

I got set back a couple months with soft epoxy problems. Probably from mixing too much hardener in with the resin. Don't want a similar "soft" rerun with my varnishing too. Teardrop building boo boos are real frustrating. I really, really want to go camping this spring and summer in the TD.

(Cliff, a little friendly thread hijacking by you is OK with me, as long as it doesn't stay off topic. I owe you, big thank you, for the tip on LED Littlites. Will soon test it and post how it well it works.)

[Miriam C.]

I had that problem and ended up using Minwax Clear Shield. They are canceling it so stuck for now. Used some floor finish I had left over for the inside.

If I were starting now I would use Zinsser Bullseye brand shellac. I used it for the raised bed and it seals out wood odors a lot better.

[tinksdad]

I got curious and did a little Googling about the Minwax Spar Urethane for my own benefit. I came across this link and thought about the possibilities for teardrop use. I am sure (make that hoping) that the real paint pros will chime in and give their opinion. I am always open to learning more than I all ready don't know!!
http://www.woodmagazine.com/dgroups/index.jsp?plckForumPage=ForumDiscussion&plckDiscussionId=Cat%3a8068d542-84e7-4789-9133-cb8743c46c54Forum%3a0dfd8ffc-8454-4518-a922-9eab1aed8cf1Discussion%3acbdd3b35-ef15-4729-941e-5e994902c749

[wannabefree]

I have had adhesion problems with Varathane and don't like the way it looks on the wood, so haven't used it for many years. It may have improved in 30 years, but I won't touch it. I used Helmsman on the interior of my tear and hate it, too. It takes way too long to dry. I can't speak for longevity. Another teardropper recommended Cabot varnish (Lowes). I bought a can but haven't tried it.

A good precat conversion lacquer will do fine for interior woodwork, but must be sprayed. I use Simpson, which you won't find at a box store. It's cheap, durable, and you can apply 4+coats in a day. Can't say that for varnish.

As far as what's available in the box stores, I would recommend Deft for interior wood.

I would not recommend shellac unless you are going to topcoat it with varnish. Shellac has poor water resistance. If you can keep it dry, though, it may be a good choice. It's easy to apply and easy to repair, something most finishes can't offer.

Like most things in life, there is no ideal finish. The best advice I can offer is to get a few small cans of various finishes and try them out. Unfortunately, what one person will recommend may be good for them and not for you.

[Juneaudave]

Steve...it might be good to make up some test panels with whatever you decide to use before going for it. You'll sleep alot better if you know the materials are going to work together...

[Esteban]

Steve...it might be good to make up some test panels with whatever you decide to use before going for it. You'll sleep alot better if you know the materials are going to work together...

Good idea, Dave. I planned on making test samples of some of the suggested finishes on stained birch plywood scraps. I especially want to see how well an oil base varnish coating over the Varathane water base spar varnish looks and adheres.

Prior to staining and varnishing the cabin walls birch plywood I made two sample boards to try out different stain colors. I varnished the stains I preferred with water based Varathane spar varnish. The sample boards had no apparent adhesion problem - on either a pine board or on birch plywood. I wonder why? I still have the sample boards so I'll do a scratch test on them.

Minutes later. Results of the scratch tests on my older sample boards: The varnish on the test boards seems to be harder and to adhere well enough. I rubbed the round handle of a chisel on the boards and it left dull scratch marks on the varnish surface. It did not bubble or peel off the varnish. When I used the sharp end of the chisel it scraped off some finish which felt a little soft (slightly rubbery, not dry or powdered). It did not peel it off in a layer of soft plastic kind of like soft Saran Wrap.

The test boards were varnished from a quart can. The birch plywood for the walls was mostly varnished from a later purchased gallon. Maybe it's different somehow, or was not stirred/mixed enough?

The worst case scenario I imagine would be to sand off all the spar varnish down to raw wood and then glue another layer of birch plywood on top to stain and finish. Hope not to have to go to that length.