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time between shellac and water poly finish?

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Forum topic by JesseTutt posted 05-26-2013 05:33 PM 1000 views 0 times favorited 11 replies Add to Favorites Watch
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JesseTutt

811 posts in 858 days


05-26-2013 05:33 PM

Topic tags/keywords: shellac finish dry time water based poly

I am trimming out a window with 1/4” oak veneer ply. I want to use shellac to get the warm brown look of an oil finish, but the top finish will be water based poly. With the temperature in the mid to high 70s what is the minimum dry time for the shellac before I can spray the poly on?

-- Jesse, Saint Louis, Missouri


11 replies so far

View Fred Hargis's profile

Fred Hargis

2038 posts in 1241 days


#1 posted 05-26-2013 05:52 PM

If it’s good shellac (not too old), I’d say pretty quickly. I wouldn’t be afraid to apply the waterborne the same day. Shellac is pretty much dry once the solvent has evaporated….that will happen even more quickly in warm temps. You will want that to be dewaxed shellac….

-- Our village hasn't lost it's idiot, he was elected to congress.

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JesseTutt

811 posts in 858 days


#2 posted 05-26-2013 06:05 PM

Yes I am using dewaxed shellac that I mixed yesterday from fresh alcohol and old flakes that were kept dry. Initial color test has the shellac drying without any problems.

-- Jesse, Saint Louis, Missouri

View GuyK's profile

GuyK

356 posts in 2827 days


#3 posted 05-26-2013 06:05 PM

Jesse, Fred is right, you can apply your top coat rather quickly over the top of shellac. In my shop I use a mixture of shellac and denatured alcohol. I let it dry for about 1 hour to 1 1/2 hours, then lightly sand and top coat with a water based poly. Good luck.

-- Guy Kroll www.thelandsathillsidefarms.org

View NiteWalker's profile

NiteWalker

2710 posts in 1325 days


#4 posted 05-26-2013 06:33 PM

I’ve top coated dewaxed shellac after 45min with a waterborne with no problems.

-- He who dies with the most tools... dies with the emptiest wallet.

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JesseTutt

811 posts in 858 days


#5 posted 05-26-2013 07:05 PM

Thanks All!

Follow-up question: The back side of the ply will be glued to the (birch?) plywood that came as part of the bay window. Normally I would apply the same number of coats of the same finish to the back side. In this case do I really need to shellac the back that will be glued, or is the water based poly sufficient?

Guy: I understand you to say that you sand after the shellac with a lubricant of water based poly prior to spraying poly?

-- Jesse, Saint Louis, Missouri

View CharlieM1958's profile

CharlieM1958

15795 posts in 2966 days


#6 posted 05-26-2013 07:36 PM

Jesse, maybe I am misunderstanding your question, but the main reason to finish both sides of something (other than cosmetic) is to prevent one side from absorbing more moisture than the other. If one surface is going to be glued directly to something else, there is no need for any finish at all.

-- Charlie M. "Woodworking - patience = firewood"

View Cosmicsniper's profile

Cosmicsniper

2199 posts in 1906 days


#7 posted 05-26-2013 07:55 PM

I’ve topcoated sealcoat shellac within 20 minutes here in Texas. Probably could have done it sooner.

-- jay, www.allaboutastro.com

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GuyK

356 posts in 2827 days


#8 posted 05-27-2013 01:53 AM

Jesse, what I do is lightly sand the shellac then use a water based poly as the final coat.

-- Guy Kroll www.thelandsathillsidefarms.org

View NiteWalker's profile

NiteWalker

2710 posts in 1325 days


#9 posted 05-27-2013 02:01 AM

I sand the shellac with 320 before spraying the wb poly.
On the insides or non-show sides of things I do spray the shellac, but only 1 or 2 coats of wb poly. Otherwise it’s a waste.

-- He who dies with the most tools... dies with the emptiest wallet.

View JesseTutt's profile

JesseTutt

811 posts in 858 days


#10 posted 05-27-2013 04:01 AM

NiteWalker: why the shellac on the non-show sides? Won’t the wb poly seal the wood?

-- Jesse, Saint Louis, Missouri

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NiteWalker

2710 posts in 1325 days


#11 posted 05-27-2013 05:35 AM

I do it because the wb poly alone would raise the grain more than the shellac. So after the first coat I’d have to sand a bit more. The shellac raises it very little; a light swipe with 320 and it’s ready for poly.

But if saving time is the objective, wb poly alone works fine. On things like small cabinets or shelves it actually helps. The wb poly gives the wood no color at all, so it’s a tad brighter than with a coat of shellac first. This helps keep the interior looking bigger than it is.

But since I have the shellac in the gun and it doesn’t take a whole lot to spray a quick coat on insides/no-show sides, I do it.

-- He who dies with the most tools... dies with the emptiest wallet.

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