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White film forming over a freshly shellac'ed surface??

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Forum topic by Vrtigo1 posted 937 days ago 1513 views 0 times favorited 16 replies Add to Favorites Watch
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Vrtigo1

430 posts in 1615 days


937 days ago

I’m building a pine rocking horse and sprayed it with amber shellac. The first coat went on nicely a couple days ago, tonight I sprayed the second coat and noticed that about 3 hours after I sprayed it, it started to form a white film over the shellac.

I sprayed both sides of it in my driveway at dusk and left it out for about half an hour to dry. After I sprayed the first side, I flipped it over and set it on painter’s pyramids and sprayed the other side. When I brought it in, I noticed that some condensation had formed on it so I wiped it off with a clean rag and it looked fine. The film is only forming on one side, the side that was up. The side that was facing down still looks good. There was no condensation on the bottom side, so I’m guessing the condensation on the top must be what caused this.

Is there anything I can do to fix this short of sanding the finish off and starting over? I’m hoping I don’t have to do that because I’m making this for my son’s first birthday which is on Saturday and refinishing is going to put me in a time crunch. Any help will be appreciated!


16 replies so far

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1736 days


#1 posted 937 days ago

I had something similar happen once. I just sprayed another coat of thinned shellac over it and it went away.

If I understand correctly, the film is moisture trapped in the shellac when the alcohol dries. Spraying when it is dry allows the new coat to dissolve the previous coat and release the moisture. Worked for me anyway.

View AaronK's profile

AaronK

1395 posts in 2088 days


#2 posted 937 days ago

yeah, the good thing about shellac is that you can do that. poly is a lot more difficult :-)

View Loren's profile

Loren

7385 posts in 2271 days


#3 posted 936 days ago

It will probably gas out and vanish. I’ve had blushed shellac do
that before. Just give it up to a week to see if it improves. Or
apply another thinned coat and see what happens.

-- http://lawoodworking.com

View JAAune's profile

JAAune

771 posts in 940 days


#4 posted 936 days ago

If it’s cold or very humid or the shellac was applied too thick it’s likely to do that. If the environment is unfavorable one good way to avoid problems is to warm up the shellac. My favorite method of warming shellac is simply to get a container of steaming hot tap water and place the jar of finish inside.

-- See my work at http://remmertstudios.com and http://altaredesign.com

View Vrtigo1's profile

Vrtigo1

430 posts in 1615 days


#5 posted 936 days ago

Thanks for the advice, one question though. When you guys say to apply a thinned coat of shellac, can you give me some more info on what you mean when you say to thin it? Do I just thin it by adding some alcohol to it? How much should I add? I’m just using the can of shellac you can buy at home depot.

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JAAune

771 posts in 940 days


#6 posted 936 days ago

Depending upon the can you bought it’s probably 2-3lb. cut. Most people seem to prefer 1lb cut since it is much easier to apply. The article linked below will give you more information on this.

My preference for pre-mixed shellac is Zinsser SealCoat. It is waxless and has a shelf life of three years from date of manufacture. I think their cans are labeled too so you won’t have to take a chance of getting old stuff when buying the product.

Here’s an article to read on the topic. It gives a better explanation and more facts than I could put together on short notice.

Fine Woodworking on Shellac

-- See my work at http://remmertstudios.com and http://altaredesign.com

View Lifesaver2000's profile

Lifesaver2000

512 posts in 1736 days


#7 posted 936 days ago

When I was spraying shellac originally I cut the Bullseye shellac from Home Depot 50/50 with denatured alcohol. When I sprayed over it the time it had blushed, I cut that mix in half again, so 25% shellac from the can, and 75% denatured alcohol. Since the shellac dries so fast, the results were apparent right away.

In my case, I had been spraying all day with a light coat about every 30 minutes, when it started one of those foggy, heavy rains. I thought that I could get that last coat on, but after I finished and went back to check on it, I saw that foggy look. Of course, it was the last coat I planned to spray. I just had to wait until a day when the humidity wasn’t at nearly 100%, spent a few minutes spraying that thinned coat, and had the problem fixed in no time.

I have to admit it had really worried me until I did some research online and saw how simple a fix it was, so that actually doing it was kind of anti-climatic. I had also worried I might have to sand down and start over, but it turns out this is a pretty common problem with an easy fix.

View Sawdust4Blood's profile

Sawdust4Blood

346 posts in 1645 days


#8 posted 936 days ago

Definitely need to be cognizant of environmental conditions when spraying any finish. As others have pointed out, too much humidity will cause the haze you experienced. Conversely, if it’s too hot the surface dries before the finish below can out-gas and bubbles form.

I find that thinning the 2-3lb cut you get in pre-mixed cans will make it spray easier. Also very important to check the manufacture date on the can. As shellac ages it goes through a process called esterification and that will also adversely effect your finish. That’s why I prefer to buy shellac flakes and mix my own as I need it. You’ll be surprised at how much better fresh mixed performs.

-- Greg, Severn MD

View thedude50's profile

thedude50

3511 posts in 1101 days


#9 posted 936 days ago

at the very worst a quick sand with 400 abralon or wet dry and apply a coat in the sun or under artifical light that is hot i use metal halide lamps in the shop when i am painting and shellacking it keeps the shop at 70 degrees in no time i don’t worry too much about moisture if it is warm enough i dont make a finish coat a spit coat but that is my first and second coat I hope this helps

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech

View CharlesNeil's profile

CharlesNeil

1127 posts in 2494 days


#10 posted 936 days ago

what you have is called blushing, it where the finish is absorbing moisture, either from the enviorment or from your application, ie: if spraying and you have moisture in the air line, it often will dry out, if not a light coat of very thing shellac ( 1/2lb) will usually clear it, the reason for the thin coat is more so the alcohol , which will reopen the finish and allow the moisture to escape, dusk and dawn being often the most humid parts of the day are often the worst time to spray outside

View kizerpea's profile

kizerpea

746 posts in 991 days


#11 posted 936 days ago

i had that happen to. i dusted it with 100% denatured to open up the finish an that done it…

-- IF YOUR NOT MAKING DUST...YOU ARE COLLECTING IT! SOUTH CAROLINA.

View Vrtigo1's profile

Vrtigo1

430 posts in 1615 days


#12 posted 936 days ago

Thanks all for the replies. I was worried this was going to ruin my project. I ended up spraying another coat this afternoon before I got online to read the replies here, so I just dialed the air way down and sprayed a very thin coat. It took 2-3 coats with 20 mins in between but the problem is completely gone now.

Unfortunately, dusk is my prime shop time since I get off work around 6 and have an hour or so before the wife and kid come home, so I have to fit what I can into that hour :)

Good to know that many folks recommend thinning the shellac from HD. This was the first time I’ve sprayed shellac and I was pretty pleased with how it came out. Nice to know that it will be even better next time when I thin it out some.

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thedude50

3511 posts in 1101 days


#13 posted 935 days ago

THERE IS A GUIDE TO SPRAYING THIS FINISH ON ONE OF THE MAGAZINE SITES I THINK IT WAS ON WOOD MAGAZINE SITE IT TELLS YOU HOW MUCH ALCOHOL TO HOW MUCH SHELLAC

-- when I am not on Lumberjocks I am on @ http://thisoldworkshop.com where we allow free speech

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Vrtigo1

430 posts in 1615 days


#14 posted 935 days ago

I looked at the can and couldn’t find any info on what cut it is. I also noticed that it says DO NOT THIN in all caps on the label. This is the standard zinnser bullseye shellac off the shelf at home depot. Should I ignore the label? I need to spray a final touch up coat.

View AaronK's profile

AaronK

1395 posts in 2088 days


#15 posted 935 days ago

yeah, they all say “do not thin” :-) probably because they want to sell you more, and maybe because of lawsuits. anyway, you can thin them all!

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