Epifanes over shellac - Woodworking Talk - Woodworkers Forum
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post #1 of 12 Old 06-25-2019, 09:48 AM Thread Starter
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Epifanes over shellac

I知 finishing a chaise lounge for my deck. I知 using African Mahogany and just put a 1# cut of dewaxed shellac on it. Since it is already in sub-assemblies, do I need to hit them with a scuff of 320-400 grit, or can I spray the Epifanes spar varnish over the unsanded shellac, which feels a little rough, as all shellac does?
Thanks for any guidance.


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post #2 of 12 Old 06-25-2019, 09:56 AM
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I use a lot of Epifanes - but have never applied it over shellac.
I would do several practice boards to be really comfortable with it.
[shellac is strictly an interior product - not for outside projects].
there is a big learning curve with spraying "varnish" as opposed
to spraying polyurethanes. if you do spray it, don't get frustrated
with the drips and runs - just address them with a paint brush.
keep in touch - this type of project comes up regularly.
and as a note: there is no clear finish that will give you UV protection
for years and years. Spar Varnish has to be applied to at least 5-8 coats
[minimum] to be totally effective against the damaging UV elements.
and a maintenance coat every couple of years.
ALL clear coats are maintenance - maintenance - maintenance until it dies.

.

.
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Last edited by John Smith_inFL; 06-25-2019 at 10:22 AM.
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post #3 of 12 Old 06-25-2019, 10:16 AM
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Somewhere you should be able to contact tech support at Epifanes and ask them if it can go over shellac. Then you will know for sure.

My question is : why would you put an inferior finish down first and cover it with a good one? Like building a very stout structure on a very weak foundation.
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post #4 of 12 Old 06-25-2019, 10:48 AM
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I'm with John's concerns about using shellac on an exterior application, even if top coated.


But to answer your question, yes, you should sand shellac between coats.
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post #5 of 12 Old 06-25-2019, 11:20 AM Thread Starter
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Epifanes over shellac

I知 not really worried about the shellac holding up under the Epifanes. I put it on to enhance the grain. If the shellac fails, then the Epifanes isn稚 doing its job. My only concern is leaving the shellac unsanded and rough, then applying the Epifanes. Wondering if it would make the Epifanes rough also. I should try a couple test boards and call Epifanes.


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post #6 of 12 Old 06-25-2019, 11:44 AM
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The epifanes would have enhanced the grain as much as the shellac and epifanes will adhere to either standard or dewaxed shellac but shellac is an interior finish. It's destine to fail. Given the cost of epifanes it would be cheaper and easier in the long run to strip it now and just use the epifanes.

You have to understand exterior wood expands and contracts more than interior wood. Therefore finishes intended for exterior use are made elastic enough to deal with the wood movement. If you use an interior finish outdoors even if you cover it with glass it will crack and lift because it has been formulated to be hard and rigid. The epifanes might help but when a finish starts lifting water tends to get under the finish and expands the lifting and rots the wood in the process.
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post #7 of 12 Old 06-25-2019, 12:29 PM Thread Starter
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Thanks all. Looks like I値l be stripping and redoing.


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post #8 of 12 Old 06-25-2019, 01:21 PM
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I've used shellac in various forms for almost 50 years on outside wood projects to give color to the wood, then sealed with either varnish or poly. Never a problem. The top coat never peeled or distressed.

Go ahead and try it. No reason to strip provided you've applied the shellac in thin coats and it's dry.

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post #9 of 12 Old 06-25-2019, 02:59 PM Thread Starter
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Yes SCHZ,
I only put a thin 1# cut of Sealcoat on the sub-assemblies, however sanding between the slats is proving to be a pain!!!


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post #10 of 12 Old 06-25-2019, 05:24 PM
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Quote:
Originally Posted by jg2259 View Post
Yes SCHZ,
I only put a thin 1# cut of Sealcoat on the sub-assemblies, however sanding between the slats is proving to be a pain!!!


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You should be fine. In this case, provided your applied the shellac to a smooth surface, your sanding doesn't need to be severe.

Actually, a brown paper bag would do to knock down any nibs. I use grocery store brown paper bags all the time after shellac dries. Never a problem.

If your surface was smooth before you applied the shellac, a brown paper bag will do the trick quickly. No need for sandpaper.
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post #11 of 12 Old 06-25-2019, 07:23 PM
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Years ago... I was told by a window maker to use shellac on the wood to seal it prior to installing the glass into the bare wood. He said it would seal the wood prior to caulk and paint.
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post #12 of 12 Old 06-25-2019, 10:41 PM
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If jg2259's project just has a thin coat of shellac it should be alright with the epifanes. It's just if there was a coating on the surface enough to crack it would be a problem.

You have to be careful using shellac with other finishes. Back in the 1950's and 60's it was common to have real wood knotty pine paneling. The painters would to through and coat the paneling with a coat of shellac to seal in the sap before applying a varnish. Varnish will adhere to standard shellac without a problem. Now if you were to do the same thing today and use an oil based polyurethane it would peal off. This is the main reason a de-waxed shellac was developed. The natural wax in shellac interferes with the adhesion of polyurethane. Old fashion varnish will still work but not poly. Also a de-waxed shellac can be used as a sealer for water based paints. It's kind of become a universal sealer. It's just for exterior use there can't be enough on the surface to crack. Personally I would just thin the exterior finish you are using so there is just one product on the wood.
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