09-01-2010 08:16 AM
I have been using the ZAS for Red Oak trim work and like it very much. But I have some issues with blotchyness in some parts. I have tried wiping it on and brushing it on(foam brushes as I have a couple bags of them in my finish cabinet), but it seems that I end up with some uneveness here and there. Is this an issue of the tint/shellac mix setteling and needing to be mixed continually or maybe I am putting it on unevenly? Also, how can I even these areas out as I have tried to sand them down but still have the discoloration. I am also using Zinsser Clear Shellac on Walnut as accents in the trim work, but no issue there at all, so I am thinking it just dealing with the pigment.
09-01-2010 08:33 AM
Let me guess: the lap marks are darker?
I spray shellac almost exclusively because of this. If you've got a 25-gal compressor and a small detail cup gun - about $30 or so, I have two inexpensive DeVilbiss guns among others - this should fix you up. Dial the pressure down to about 25-30 PSI at the compressor and practice on a board or six and then have at it.
Spray lightly, don't pile it on. Whisper thin coats are what you want. Recoats can happen in half an hour. You should like what you see - and no lap marks!
Wood Online Moderator
09-01-2010 10:45 AM - edited 09-01-2010 10:52 AM
How much were you thinning the shellac. It is mostly found at three pound cut, and should be substantially thinned with denatured alcohol. Using more coats to achieve the same thickness will let you even out the application. I like 1 1/2 pound cut for wiping. To get this mix 3 parts of alcohol with 2 parts of the canned Amber shellac. But the measurement isn't at all critical. If you are off it will hardly matter, shellac coats all fuse together anyway.
By the way, scrap the foam brushes. It's just very hard to get an even coating with them. I like awatercolor wash brush with taklon gold bristles, but others don't because they do provide a small reservoir so you have to dip them often. Soft mop brushes with fine bristles are recommended by others. But, wiping with cloth works well. Fold into a pad so that there aren't loose ends.
09-01-2010 11:31 AM
Spraying is not an option right now in my garage, so I am stuck with hand application.
I made the extrodinary assumption that it was for use straight from the can. Ok, I can do that as well as getting some brushes.
09-01-2010 12:11 PM
Yup, it is almost always thinned. Part of the reason, besides tradition, that it is sold in such heavy cuts is that shellac has a longer shelf life when it is more concentrated. Pre-diluted to 1 1/2lb. cut would mean more problems with shellac dying in inventory.
09-02-2010 04:52 AM - edited 09-03-2010 02:39 AM
…that I believe we need to address. In your question you wrote, in part:
“Is this an issue of the tint/shellac mix settling and needing to be mixed continually or maybe I am putting it on unevenly?”
There is no “tint” mixed with shellac. The color of the various shellac grades is the result of the extent to which the refining process has removed the dye that occurs naturally in shellac. Seedlac and the garnet grade contain the most natural dye while super blonde contains the least. The color in shellac is not pigment, it will not settle out and it need not be stirred.
“Also, how can I even these areas out as I have tried to sand them down but still have the discoloration?”
Glitches can be sanded; but, since shellac is so hard it takes a very long time and clogging of the paper is almost a given, even when using open-coat sandpaper. The problem is that heat generated from sanding, especially power sanding, will melt the resin causing it to gum up the paper. A better removal alternative is by scraping. For runs, sags and brush overlaps as alluded to by Matt, a stiff trapezoidal utility knife blade held between your thumb and forefinger makes an excellent scrapper. If the defect is physical noticeable (you can feel it) you can first lightly moisten the area with denatured alcohol, allow the shellac to soften just a bit and then scrape away the problem.
The best way to deal with these problems is to remove them as they occur. When I apply shellac with a brush I keep a soft cotton cloth dampened with denatured alcohol or, if brushing a darker shellac grade, a bit of shellac in my free hand. As run, sags and unintended overlaps occur I simply wipe them away with the rag and continue brushing.
“I am also using Zinsser Clear Shellac on Walnut as accents in the trim work, but no issue there at all, so I am thinking it just dealing with the pigment.”
You are dealing with color; but, you aren’t dealing with “pigment” (see above). The color build-up is the result of uneven shellac application. That uneven application is directly related to your technique. To parrot an earlier reply, lose the foam “brushes”. I have never seen a finish application where the use of a sponge-on-a-stick produced superior results to a bristle brush or appropriate wiping technique. The most prominently advertized attributes of these “brushes” is that they are disposable. In my view, that is their best and only attribute…so, dispose of them.
Shellac, when brushed, must be flowed on quickly with a little overlap at the wet edge, and as little back brushing as possible. Some runs, sags and heavy spots are bound to occur. As they do, remove them immediately as described above. Wipe the area with a soft cloth dampened with denatured alcohol, or the shellac you are brushing. (Please note, I said “dampened”. You don’t want so much alcohol in your rag that you thin the shellac causing it to run.) My preferred brush is a natural bristle brush with long, soft fibers (I’m sorry, I don’t recall the brand or model and I can’t look at the brush since I’m away from my shop until next Wednesday). In my view the reservoir in the synthetic bristle brushes, even the expensive Taklon artist brushes, lack any meaningful reservoir. As a result you will make more frequent trips back to the shellac container. These brushes also unload almost immediately on contact. The combination of the two (no reservoir/quick unload) can add to the problem of uneven application.
As to the “cut” of shellac being brushed, while I would agree that a two-pound cut is adequate for your application, I do not subscribe to the idea that thinning makes brushing easier. Consider for a moment that brushing shellac is made difficult, relative to other finishes, because it dries so quickly (alcohol evaporates very quickly). How then do we solve the problem of rapid evaporation of alcohol by adding more alcohol? All we do when we add alcohol to shellac is reduce its “cut”; the amount of shellac resin present in a given volume of liquid we apply. While it may be true that applying less resin per brush load seems to lessen the problem of the “blotching” you describe, the ultimate result of thinning is that you have applied far less useful finish. Remember, all of the alcohol is going to evaporate. It is only the shellac resin left behind that contributes to your finish. The solution to the problem is to control the drying (evaporation) rate of the shellac. This is easily accomplished by the addition of one table-spoon of pure gum turpentine per quart of shellac to whatever cut you are brushing (not mineral spirits or paint thinner, but pure gum turpentine; also a vegetable distillate that will incorporate easily with denatured alcohol). The turpentine will slow the evaporation rate of the alcohol thus giving you a longer open time and better flow-out. The small volume of turpentine added will do little to diminish the amount of resin you apply. Using this technique I have successfully brushed shellac mixed in a five-pound cut (which was the cut regularly employed by the “old-timers” finishing floors and millwork prior to the advent and unfortunately wide-spread use of polyoneverythane).
As an aside, I find “wiping” equally problematic if by “wiping” we simply mean dipping a soft cloth in liquid shellac and wiping it on. This technique is again only successful if you are applying a very light cut (very little shellac resin dissolved in lots of alcohol). This technique works because very little actual finish is being applied. Taken to its logical extreme, one can wipe alcohol over all manner of surfaces without ever experiencing so much as a minute “drag” on the applicator. It is the addition of dissolved shellac resin to the liquid that produces the problem. Of course, it is also the introduction of shellac resin that produces the desired finish. Padding (as opposed to simple wiping) can easily and effectively applied to any cut of shellac with desirable results.
09-02-2010 11:16 AM
Thanks for the information. Since I am new to shellac I was thinking that the amber coloring was added, so now I know. I did thin out the ZAS with some denatured alcohol and used a brush for application with much better results. With things so warm in my garage the shellac was drying out too fast, but now with it thinned a bit I can get good covering and blending without it drying out on me.
As for the turpintine, I haven't seen that stuff in years and is probably more of a speciality item these days and not a typical Home Depot or Lowes item. But I will look around and see if I can find some.
Thanks for the help!
09-02-2010 11:52 AM
Try Michaels or Hobby Lobby, over by the fine oil painting supplies for gum turp. I've got an old (really! old) container and that's where I got it. I'll be replacing it with fresh stuff before I try this.
Wood Online Moderator
09-02-2010 12:23 PM
I have a Michaels just down the road so I will check with them.