LumberJocks

Sanding after initial shellac coat gumming up...

  • Advertise with us

« back to Finishing forum

Forum topic by widwotkma posted 946 days ago 3657 views 0 times favorited 14 replies Add to Favorites Watch
View widwotkma's profile

widwotkma

32 posts in 989 days


946 days ago

Topic tags/keywords: maple sanding shellac

I made a cross as a Christmas present for my parents out of figured maple and purple heart. The cross itself turned out reasonably well, considering it was my first such project. The cross is essentially made up of 7 pieces of wood glued together.

Maple cross w/ purple heart

I wanted to “pop the grain” so after sanding to 200 grit, I applied a coat of Zinsser Bulls Eye Seal Coat (dewaxed shellac) mixed with about 7 drops of TransTint. After that dried, I tried sanding with 220 grit, but got globs that built up on the surface. I was able to remove them carefully using a razor blade, but am now uncertain what to do to get to the next step (the plan is to add several coats of an oil based finish (varnish).

Note I have another Christmas present project (this one a box – also done with the maple and purple heart, plus a lid of ambrosia maple) and I applied the same initial finish. I have not yet sanded it, in hopes I can avoid having the same issue with it.

Ambrosia maple lid

Maple box w/ purple heart keys

Any thoughts/ideas/tips/tricks would be much appreciated. I’m obviously quickly running out of time to finish these!

Thanks much


14 replies so far

View Gary's profile

Gary

6973 posts in 2030 days


#1 posted 946 days ago

How long did it dry?

-- Gary, DeKalb Texas only 4 miles from the mill

View jmos's profile

jmos

681 posts in 967 days


#2 posted 946 days ago

My understanding is shellac will do that if it is not completely dry, or if it is old. If letting it dry longer doesn’t do it, you can remove the shellac with denatured alcohol. A good rub down may remove enough to let you reapply fresh shellac, or try another finishing method.

-- John

View PurpLev's profile

PurpLev

8476 posts in 2246 days


#3 posted 946 days ago

sounds like the shellac did not fully dry yet. how long did you wait before you sanded the shellaced piece?

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View widwotkma's profile

widwotkma

32 posts in 989 days


#4 posted 946 days ago

Thanks so much for the quick responses.

I had let it dry overnight thinking that would be long enough, but maybe not. The can of shellac is new (purchased several weeks ago) so I don’t think it is an age issue. Does temperature have any impact? My garage is not heated and it has been in the 40’s lately.

I will try to remove the shellac from the cross with denatured alcohol, resend and start over. I have let the box dry several days now and will try sanding it tonight to see if I have better luck. I’ll keep you posted…

View trophy's profile

trophy

8 posts in 1675 days


#5 posted 946 days ago

With your unheated garage and low temperature you will need to move the items into a warm DRY area for the finish to cure properly. Dampness, as well as temperature are also big no no’s with shellac as it will not cure properly and will remain gummy. Your projects are very nice and will look great once you resolve the shellac curing problem which in my opinion is environmental. You still have ample time to refinish them, jmos is correct with using the alcohol to remove the shellac as a starting place. Good Luck and Merry Christmas

-- Bruce, Upstate New York

View jmos's profile

jmos

681 posts in 967 days


#6 posted 946 days ago

You might also want to try bringing them inside overnight. Temperature always effects drying time, lower is slower, but too hot can cause issues as well with some films. There is a significant difference in the vapor pressure of denatured alcohol between 40 and 70 degrees F. But, I would have thought overnight would have done it, even at 40deg F…

You might also want to check the date on the can; new from the store doesn’t always mean a new can.

-- John

View Alan Robertson's profile

Alan Robertson

66 posts in 2516 days


#7 posted 946 days ago

Been using shellac for awhile. Don’t panic, you’ve got a good base/sealer coat. Lightly sand high spots, (you would do this any way). If you haven’t sanded thru to bare wood—apply denat-alchohol to old t-shirt (wet) and start wipeing down the cross and box. The wipeing will soften the shellac and smooth it out, maybe giving you the base you want. I use this method for hand rub finishes.
After wiping (no sand) let dry.
50/50 mix———-turpentine or paint thinner or mineral spirits and polyurethane
brush-wipeon let firm up wipe off all excess repeat wait 12 to 24 hrs wax/buff
IMPORTANT KEEP WARM TAKE BUFFING & WIPEING RAGS OUTSIDE AFTER USING

-- MrAl

View widwotkma's profile

widwotkma

32 posts in 989 days


#8 posted 946 days ago

Thanks all, this has been extremely helpful and insightful. I have to wonder how people learned this stuff before the age of the Internet?!

I’ll post some pics of the final products. Hopefully they will turn out ok, but as this is my first batch of “real projects” I’m sure I have much more to learn the hard way. But that is part of the fun…

Merry Christmas!

View Kent Shepherd's profile

Kent Shepherd

2697 posts in 1883 days


#9 posted 944 days ago

Nothing against shellac, but if you are using an oil finish for the top coat anyway, you could use Tung Oil, Boiled Linseed Oil, etc, to pop the grain. That’s what I am using on my boxes and it works well. I usually thin it with mineral spirits, but have also used it straight out of the can. You can come back with the next coats quicker this way.

I agree with everyone on the drying time. That is usually what makes a finish gum up like that.

-- She thought I hung the moon--now she just thinks I did it wrong

View yooper's profile

yooper

181 posts in 1424 days


#10 posted 944 days ago

I highly recommend Arm-R-Seal by General Finish. I have used Seal Coat Shellac and BLO, but was blown away by how easy Arm-R-Seal is to use and how nicely it finishes. It contains BLO I believe, so it pops the grain nicely.

-- Jeff, CT - better late then never

View JasonD's profile

JasonD

180 posts in 1459 days


#11 posted 944 days ago

Shellac is a great finish, but you can’t always trust the premixed can stuff. Just because you bought it from the store recently, it could have been sitting on their shelves for quite some time before you picked it up. There is a date stamp code on the can (should be about 5 or 6 numbers).

Also, I’ve had cans of Zinsser that were only about 6 months old according to the date code, but when I tried to use them, it was clearly bad. One thing you have to consider is that with the premixed stuff, no matter how old it is, we don’t know what kind of conditions (ie: temperatures) it was exposed to in shipping, warehousing, etc.

Mixing your own shellac from flakes is really easy and costs less than buying premixed. Plus, you have the benefit of only mixing what you need for a given project. So, you don’t have to worry about it going bad before you use it. Check out shellac.net. They have great prices and their customer service is outstanding. With some flakes, denatured alcohol from a local hardware store, and a $20 kitchen scale from Walmart, you’ll be in business.

I put off trying to mix my own for a long time; worried that I’d mess it up, but it’s ridiculously simple. I’m kicking myself for not trying sooner. If you have any questions, don’t hesitate to ask.

Btw, beautiful work on the cross and box!

View Tennwood's profile

Tennwood

100 posts in 1778 days


#12 posted 944 days ago

I love shellac because I can finish a project very quickly with a great finish. Like JasonD, I usually make my own, but you shouldn’t have this problem with the pre-mixed either. One trick I was taught was to wipe the wood down with mineral spirits once the shellac is dry. Then while it is wet with the MS, sand it using a 600 grit wet/dry sand paper instead of the 200 grit you are using. The 200 may be too aggressive for the sealer and it may not be totally cured. I can usually apply a coat every 30 – 60 minutes using this method. I’ll wait a day for my final coat. My shop is in the basement so I am sure having a constant temperature helps.

-- Jim, SE Tennessee, "Don't spare the kindling Dear, we have plenty"

View JasonD's profile

JasonD

180 posts in 1459 days


#13 posted 943 days ago

Tennwood, I agree the premixed shouldn’t gum up on him like that, but that’s assuming it’s still good. I’ve had some premixed that went bad on me before and it acted just like he’s describing above; stayed tacky, never fully hardened even after all the alcohol evaporated. The date on the can said it was only 6 months or so old, but when I asked someone more knowledgeable than me, they brought up the point that if it was exposed to higher temps for long periods of time during shipping, warehousing, etc., it could have gone bad.

View superstretch's profile

superstretch

1482 posts in 1290 days


#14 posted 942 days ago

I had some problems with an old can of wipe on poly I had this past week.. In some cases, I let it dry for about 40 hours and it still gummed up. What I found best was to take it back down to raw wood with some 0000 steel wool.. It doesn’t gum up, doesn’t mar the wood, and chews through the finish pretty quickly.

In some cases, I opted to not use the poly again and just wiped it down (and waxed a few of them).

The finished appearance was superb

-- Dan, Rochester, NY

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase