In another thread, Russell Neyman suggested that we start a discussion on CA finishes, so here it is. Sorry if it is a little long.
I don't like finishing, especially when it takes more than a day, so I started using CA, even on bowls and platters. Although the CA application is only done in small sections (bands), it goes pretty quickly. I can do one coat on a gouge handle in less than a minute and typically end up with six coats. Although the finish can be anything from satin to glossy, it does not look thick or plastic. There were lots of mistakes and learning, but the following has worked well for me. It is based on a couple of techniques that are a little different from other CA finishes.
- This is for finishing on the lathe because it requires the high speed and friction to achieve the smooth surface.
- Sand the wood, not the finish. Unlike typical CA finishes where a thick coat is applied and then sanded flat, this finish depends on a very smooth wood surface and eliminates any sanding of the finish.
- Use boiled linseed oil (BLO) both as a base/sealer coat and as a lubricant (?) when applying the CA. Apparently, BLO is chemically compatible with CA and does not interfere with it curing, other than slowing down the process. I think it also acts as a lubricant, much like the walnut oil used in a french polish.
- Use paper towels for all applications. Test the CA on the towel, and if it starts smoking (curing) immediately, find a paper towel that doesn't do this.
- I use thin CA. I have tried medium and thick to build coats faster, but they seem to dry too quickly and form "smears" rather than a smooth glossy surface.
First, sand the wood through 1200 grit with sandpaper and then finish with 2000 and 4000 grit Abralon. It should have a nice uniform sheen at this point. After sanding, wipe the surface liberally with BLO, wipe off the excess and burnish it dry with a folded paper towel at pretty high speed (1500 RPM for spindles, less for bowls and platters). The surface should dry and not be tacky - burnish more if it is. Incidentally, this really brings out the chatoyance, more than any other finish I have tried.
PUT A GLOVE ON THE HAND APPLYING THE CA!!!! The CA is now applied using a paper towel folded to about 3/4" wide strip about 4" long. Do this by putting a drop of BLO on the tip of the towel and then the CA, about a 1:1 ratio (hard to tell since the CA soaks into the towel). With the lathe running, apply the CA/BLO mixture in a small band 1" - 2" wide. Rub back and forth quickly as it cures. Watch the wood surface in the reflection from the work light and you will see the lines from the liquid disappear and the surface should become very glossy. Some say not to do this as it melts the CA. I think the smooth surface is a result of the burnishing. The towel will get hot and stiff from the CA and probably stick to the glove (I use finger cots on top of the glove finger and replace them, since they are much cheaper than a glove). Cut off the end of the paper towel for a fresh section. Do not reuse the stiff towel for the subsequent coat. I do 2 coats and then hit it with accelerator. This will cause the surface to haze a little, but it will return to glossy with the next coat. As I get to the 4th - 6th coats, I cut back on the BLO so there is just a small amount compared to the CA. If the CA starts to cure too quickly and haze, increase the BLO.
If all has gone correctly, you should have a pretty glossy finish with no further sanding or buffing. If you want a really high gloss you can buff immediately with tripoli and carnuba, although I normally wait 24 hours. I keep the BLO and CA in small squeeze bottles to apply to the folded paper towel. If you get any streaking or hazing while applying the CA, just sand it back to uniformity with 400 grit and start applying the CA again. I have applied the finish by hand (off the lathe) to the bottom of pieces that could not be rechucked, but needed to use more BLO to prevent streaking and hazing, since you don't have the benefit of the high speed on the lathe. You just have to rub a lot to get it to cure.
If you want to try this, do it on a 1" or 2" spindle - that's the easiest way to start. I have attached a picture of a 10" jatoba platter that took about 30 minutes from start to finish (pun intended) to apply the CA. The picture does not show the surface well, but is is buffed to a very high gloss and the chatoyance is beautiful. I would like to hear about other's experience with CA finishes or any comments on this technique.
Dave
Jatoba Platter sm.jpg
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