Shellac Frustrations

[Dan McCallum]

Banging my head against the wall recently, I built a simple shelf out of walnut, planed and scraped it, then finished it with 600 grit sandpaper.

I did a cherry shelf a couple weeks ago the same way and it worked like a charm.

Here's the problem on the walnut: I padded on shellac (1 lb cut), but noticed it was drying streaky. I was using a old cotton tee shirt like I have many times in the past. I carefully fold up a smaller piece, then wrap it up in a larger piece (no wrinkles), soak the whole thing in alcohol, then dip it in the shellac and pad away. Always worked perfect for me in the past. This time, mulitple coats, still streaky.

So I stopped using 99% rubbing alcohol to dampen the pad, switched to shellac reducer. No difference.

Then I made up a fresh batch of shellac from flakes, again a 1 lb cut, still no difference.

Then I switched from using an old tee shirt to using an old pillow cover, still no difference.

Not sure where to turn next, other than maybe something other than shellac!

Dan

[Nelson Howe]

No expert here, but I just sealed a chest of drawers with shellac from flakes, and here would be my suggestions:

You say rubbing alcohol. You should be using denatured alcohol, I believe. My understanding is that there is more water in rubbing alcohol.

When I did it, I didn't dip my pad in the shellac. I used a squirt bottle, and when the pad felt dry, I unwrapped it and squirted the shellac into the inner pad. My understanding is that the pad should not be so wet that the shellac wants to drip if you squeeze very hard.

I doubt the make up of your pad is a problem, but I have been using cheese cloth for the core and old sheet on the outside.

The descriptions I have read (go to homestead finishing for a description http://www.homesteadfinishingproduct...adshellac2.htm, and finewoodworking dot com for some videos) also have you go across the surface in sweeping, slightly overlapping strokes from the top to the bottom, and then starting again and going over and over from bottom to top until your rubber starts to drag too much. Then let it dry and come back. It sounds to me like you're trying to apply too much too fast and causing the streaks. When I put it on, it seemed like almost no material was going down with each stroke. After time, it builds. Slowly.

Good luck,

Nelson

[glenn bradley]

+1 on DNA although the shellac reducer may be purer than that. You do not state if you removed the previous attempt before the next attempt; I would do this if you are not. The only time I get streaks with shellac is when trying to lay it on too thick. "Too thick" is a subjective term based on your cut but, suffice to say that you should be applying the thinnest possible coat.

[Prashun Patel]

Perhaps you just haven't put down enough coats. 1#, thinned with the alcohol is going to take a while to build.

The other potential prob is that the sfc had some oil on it.

If it were me, I'd try continuing the padding with a 1.5# cut, and I wouldn't precharge my pad with alcohol for fear of over dilution. If this does not work, then I'd wipe the whole surface with a rag soaked in DNA, and try to remove most of the film, then scrape/resand and try again.

[Scott Holmes]

No need to remove the old shellac. Here's a link to a buddy of mine's site that talks about the best way to make and use a pad for shellac...

http://www.hardwoodlumberandmore.com...r-Shellac.aspx

The mineral oil on the outside of the pad will help with the dragging and will not hurt the shellac finish.

[Dan McCallum]

Guys,

Thanks for all the suggestions!

I did sand off the previous attempts before my new attempts so I was starting with a 'clean slate' so to speak each time.

I actually keep my shellac in a narrow necked glass bottle so I can better control the amount that goes into the pad. Similar to a squirt bottle. I don't actually dip the pad in the shellac, sorry about that.

I do wonder about the wood surface having some impurity on it, although shellac can go over or under pretty much anything so I am not sure if that would really be the case. Ditto the walnut itself, it is more of an open pore wood, but I have used shellac with great success on elm and mahogany which are also open pored.

When I was applying it, I did 'sweep' the pad on and off as prescribed. After several strokes I could feel it get a bit sticky, so I'm thinking that's a sign that it wasn't going on too thick.

Thing is, I did nothing differently this time than I have done in the past. I've used this technique with shellac in the past many times with good results. The only thing different I can see this time is the wood - walnut. My first time using it.

I've never tried mineral oil on the pad before, have read about oil being used in conjunction with shellac for French polishing though.

So, I am still not really sure what to do next other than a different finish!

Just a note on rubbing alcohol. Rubbing alcohol is available in various concentrations, I was using 99% and have used it in the past with no problems. In this case I tried with and without rubbing alcohol, and as there was no difference I concluded that it was not an issue here.

As for DNA, the 'denatured' part of denatured alcohol refers to the addition of impurities such as methanol, ethyl acetate, etc. to prevent its consumption (as it is ethanol). Shellac reducer is identical. I prefer 99% rubbing alcohol as I feel it is less toxic than DNA and works just as well for me. (Just my opinion, not aiming to convert anyone!)

Cheers,

Dan

[James White]

Deleted: Responded to the wrong thread.

[Prashun Patel]

Dan-
I doubt it's yr technique. Oil, different pad, etc just won't make a difference. You've probably discovered as have I that the technique very forgiving once you've done it a while. I'm not saying it's easy to get a perfect French Polish, but a simple, thin, streak free shellac finish is fairly easy to wipe on once you get the feel.

I think something else is going on.

Where are you applying this? What's the temp?

Have you tried doing a different piece of wood with the same batch of shellac? That will at least determine whether the wood's the culprit.

Is it possible your cut is just too thin and it's taking more coats for the walnut to absorb and seal than yr used to? What happens when you put on a few more coats?

[Howard Acheson]

What has been the temperature and relative humidity? Fast flash off finishes like lacquer and shellac can blush in certain temperature/humidity conditions.

[Dan McCallum]

Temp and humidity, I had not given that much thought. I generally try to do my finishing outside on dry days. However, I also do it in my basement shop as well. Outside the humidity will be higher and temp lower for sure this time of year (Vancouver BC). However, the effect is the same inside or out so I doubt this is the cause. I would not describe the problem as a blushing.

Prashun, thanks for the idea to try a different species. Kind of obvious, but I certainly was not thinking that direction! So I made up another pad with the same old T shirt, and tried the same shellac on a piece of arbutus (AKA madrone) which is tight grained. The shellac went on the arbutus without problem, but when I tried to put more on the walnut, it was streaky, same as before. In fact, the 'stickiness' was far greater on the walnut, I could get stickiness and streaks on the walnut after only a single stroke, take the pad immediately to the arbutus and it would go on smoothly with no streaking or stickiness.

The walnut is air dried Oregon walnut, cut by a neighbour who had a property down there many years ago. It is about 3/4" thick and has been acclimatizing to my shop for a couple years so I doubt it has excessive moisture in it.

So then I took a piece of walnut that had been purchased at a lumberyard and so would have been kiln dried. Shellac went on smooth as silk, no stickiness or streaking at all!

So my conclusion is that the problem is caused by something in the air dried walnut that causes the pad to get sticky and grabby and leave streaks.

I suppose I could sand off the shellac, then apply something like acetone to try and lift the bad stuff out of the surface of the wood, then try shellac again. At this point I am pretty tired of this project though, so rather than risk yet another failure with shellac will probably investigate an oil finish.

Thanks for all the help everyone.

Cheers,

Dan

[Dan McCallum]

Put a coat of Tried and True on it last night, worked like a charm! Back in business, few more coats and I'll be happy to get this project off my bench in a couple days.