water based finish over linseed oil

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Bob Ionta
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water based finish over linseed oil

Post by Bob Ionta »

Does anyone know if oil under EM6000 is a bad idea?

I am just finishing a walnut/engelmann OM. I'm french polishing the top but I want to use a water based lacquer for the rest. I think a coat of linseed oil would enhance the walnut tremendously so I'm wondering if it's safe to put a product like Target EM6000 over the oil. I've tried some sample boards and have not seen any problems yet but I've had a self-inflicted bad experience with a water based polyurethane over shellac on some cabinets and it took some months for the problems to become apparent.

I have a second question about EM6000. Does anyone ever brush this stuff on? I have spray equipment but I'm not very skilled at using it. I brushed the EM6000 on my sample boards with a foam brush, getting OK but not spectacular results. It seems to brush out very thin and maybe I just haven't brushed enough coats yet to get a good film thickness. Is it going to be especially difficult to get a great finish by brushing this material?
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Bob Gramann
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Re: water based finish over linseed oil

Post by Bob Gramann »

I don’t know the answer to EM6000 over linseed oil, but I wouldn’t do it because the linseed oil never really dries. I would expect adhesion problems. I use two coats of dewaxed shellac as a sealer and base coat before the EM6000.

But, I do know the answer to brushing EM6000. I’ve done it many times. In the winter, when I don’t want to open up for ventilation, I sometimes brush a project. It requires patience. I’ve gotten my best results with a very good 1” sable brush. I tried foam brushes in the beginning, but the bubbles killed that. I brush each coat as thinly as I can apply it with no going back over strokes. After 3 or 4 coats, I level sand with very fine paper. It takes 12 coats or more—as much as spraying—sometimes more if sanding goes through. This approach does a reasonably good job, almost as good as a sprayed finish.

If you have the gear and the ventilation, it’s worth conquering the spraying. Once you figure out how to set all of the controls on the gun, get the pressure right, and get the distance and arm speed right, you can lay down a glossy wet coat without runs. One minute later, it won’t look so good as the EM6000 dries, but after drying, it will be nice and even again. I generally do 6 coats, level sand (320 grit—the next coats of EM6000 burn in and hide the 320 scratches), then do 6 more coats before leveling with 800 and polishing (two weeks later).
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Barry Daniels
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Re: water based finish over linseed oil

Post by Barry Daniels »

Instead of using oil under the EM6000, how about an epoxy pore fill. That will make the grain pop.
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Marshall Dixon
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Re: water based finish over linseed oil

Post by Marshall Dixon »

Bob Ionta wrote: Tue Aug 18, 2020 10:35 am Does anyone know if oil under EM6000 is a bad idea?
It's a bad idea. It warns you on the back of the can "surfaces should be free of oil, dust and other contaminants..."

I've been using it over shellac for years and never had problems with it. I've used Zinsner's, Target Coatings proprietary water based shellac and my own shellac mixtures. I use it with their CL100 crosslinker. They claim it's good for bar top use as it's harder and more chemical resistant.

Most recently I used Z-poxy as a filler (two coatings), sanded that back, wiped it with shellac and sprayed over that. I give it two weeks minimum to cure.
Bob Ionta
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Re: water based finish over linseed oil

Post by Bob Ionta »

On the other hand, they say it can be used over oil-based grain fillers and they sell a tung oil based sealer for use with it. However, I think you all are right - plain linseed oil sounds like a bad idea. I'm turning to shellac in some form - probably just keep going with the french polish and pumice pore fill - and I'm going to at least consider spraying the top coats if my practice sessions go well.

Many thanks to all of you for the help. It's not hard to convince myself that I've got a great idea (which turns into a disaster) so it's a huge help to get advice from experienced people.
Clay Schaeffer
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Re: water based finish over linseed oil

Post by Clay Schaeffer »

"Boiled linseed oil" has driers added so it does "dry". Still I would wait two weeks and do a barrier coat of shellac before applying the top coats.
Bob Ionta
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Re: water based finish over linseed oil

Post by Bob Ionta »

Thanks Clay. Don't know why I didn't think of using a shellac barrier coat but that would be wise. As for waiting 2 weeks ... one of my motivations for using EM6000 was speed. It takes me a month to french polish a whole guitar but I can fp just the top in about a week, getting in 3 sessions each day. I am anxious to finish this guitar and hear how it turned out then move on to other projects so I don't want to spend a month or more finishing if I can help it. Wishful thinking I suppose.

I have another guitar I built last year and finished with BLO, intending to top coat it with Endurovar or EM6000. I never got around to it. It's a 7-string and I've been learning to play it and using it in my lessons (I'm the student, not the teacher). Since I'm addicted now to 7 strings and it's my only 7-string guitar I can't take it "out of service" to finish it so the oil has had a year to dry. I guess that will be my BLO & water-based top coat experiment. As soon as I build another 7 string.
Alain Lambert
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Re: water based finish over linseed oil

Post by Alain Lambert »

Please consider that linseed oil will turn quite yellow over time. Just like 'old oil paint' was doing in the past!
Bob Ionta
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Re: water based finish over linseed oil

Post by Bob Ionta »

Hi Alain, I know it gets darker and eventually quite dark. The very old examples I've seen didn't appear yellow to me but perhaps because they were on dark wood or maybe because they were so old they went beyond yellow.
Bob Howell
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Re: water based finish over linseed oil

Post by Bob Howell »

I switched to Pure TUNG oil on light wood. Over the years I have used figured Maple a lot and want oil for initial wash coat. Even driers will tint it brown. Dilute it and give it several days to dry. It is the best of naturally drying oils due to molecular structure.

I have had old linseed oils remain soft for 20-30 days but still harden.
Tung oil has short shelf life
Bob Ionta
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Re: water based finish over linseed oil

Post by Bob Ionta »

Bob Howell wrote: Fri Nov 06, 2020 9:41 am I switched to Pure TUNG oil on light wood. Over the years I have used figured Maple a lot and want oil for initial wash coat. Even driers will tint it brown. Dilute it and give it several days to dry. It is the best of naturally drying oils due to molecular structure.

I have had old linseed oils remain soft for 20-30 days but still harden.
Tung oil has short shelf life
Thanks Bob. I've used pure tung oil (from Woodcraft) by itself on small furniture items and like it a lot. I've recently used Watco tung oil (which is a mixture with mineral spirits and some other nasty-smelling stuff) on a very old floor of dark wood and I did cover it with a water based polyurethane after 72 hours. That seems to have worked out well. However, I wouldn't use the Watco stuff on a guitar (definitely not on maple or spruce) but I'd consider the pure tung oil. I have not tried putting a film finish over it on any of my furniture projects. I think I'd want to wait longer than 72 hours for that, maybe a week or even two weeks?

For this guitar I wound up using shellac under the EM6000. I did it by french polish, using pumice to fill pores. So far it looks pretty good in spite of my amateurish spray work. The shellac did pop the grain of the walnut and I eventually managed to get a few successive coats without runs. I haven't buffed it yet. I hope I got enough finish on it to buff it successfully.
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