When I say "spotty" there are speckles of little white-ish dots in places on the pen. I don't have a picture to show because when it happened earlier today, I sanded away all the CA to start again (which I haven't done yet.)
I would hazard a guess that those aren't spots in the finish, so much as spots where there
isn't a finish (or, more accurately, where the finish isn't uniform), and your sanding dust is getting trapped in them. I've had this happen a lot with coarse-grained woods, and it ends up either taking more coats of CA, or building up a few coats of CA, sanding back to the bare wood (but
just barely - the goal is to get to a point where everything's perfectly smooth, it's just easier to eyeball when you hit wood) and then coating for real.
I have heard that you shouldn't mix the different brands (which I have done, but not on these last couple of pens.)
I've heard the same thing, but I'm so sure I believe it - and certainly not in all cases. There may well be
some combinations that don't play nice together, but my regular routine mixed Stick Fast activator with BSI CA for quite a while, and I think I was also mixing 2P-10 activator with Stick Fast CA for a little while without any disasters. I've run into more problems caused by activators with too coarse a droplet size (pumps especially, but I've had some very spattery aerosols, too - I think the 2P-10 was one of them), which seems to cause the CA to set too quickly or unevenly at cause hazing/bubbling/crazing.
For finishing, is thin, medium, or thick the best choice (or a combination)?
That's a hard one to answer, since there are a wide variety of CA application techniques, and some will work better with one thickness than another, while others use a combination. Thin and medium are definitely more commonly used than thick.
My technique of the moment (which isn't
mine by a long shot, but I'm not sure who deserves the credit, so I'll pretend it's mine - don't tell!) looks something like this:
- Fold a paper town over three times, so you get a strip about an inch wide.
- Wear thin latex/nitrile gloves or finger cots on your index finger & thumb.
- Run a little bead of boiled linseed oil across the end of the paper towel (I keep some in a dropper bottle for this)
- Run a matching bead of thin CA (which, like the BLO, won't actually form a bead - so just pretend) across the BLO.
- With the lathe running around 2500rpm, rub the paper towel (the stinky yellow end, in case you lose track) quickly & repeatedly back and forth across the blank, applying light pressure, until the CA cures (your eyes might start burning, your finger might start burning, or you might just notice the paper towel has gotten stiff). The reflections off the finish should be bright and sharp - if they're foggy, you need to keep rubbing. In my experience this is better done on one blank at a time, even if you've got two on a mandrel, but YMMV.
- Cut the end off the paper towel, and repeat as needed.
I've found that this method leaves a very smooth finish and lets me skip a lot of the sanding flat that my prior technique required - sometimes I can even skip sanding completely and go straight to Novus plastic polish #3 and #2. The drawback is that it doesn't lay down a very thick coat, so filling a very coarse or open grain can be a problem, and if you
do have to sand it's very easy to cut through the the wood. It's also not great if you realize you've over-turned your blank by a few thou and want to make it up with a thick finish.
I've also tried the same technique with medium CA. It doesn't seem to build any faster (although it may fill the grain quicker), and it takes significantly longer (minutes instead of seconds) to cure, but it
does work.