Medium CA, Mercury M300M
Mercury's Medium CA is great top coat for your wood pens. Depending on the number of coats and how highly polished, it can provide a somewhat natural to a glass-like feel for your finished work. Of course, it is also excellent for gluing in the brass tubes. Mercury Adhesives manufactures their CA here in the USA, in Atlanta, GA. It is a medical grade CA that is highly concentrated and 99.9% pure. For finishing pens, just a drop or two is all that is needed for each coat.
There are different formulations for pen makers. Thin, Medium, Low Odor/Fume, & a unique High Performance that is great for oily wood. Plus, it's has reduced fumes for finishing. Another unique feature isn't with the CA, but with the bottle. Except for the jumbo 8oz refill, all Mercury CA is packaged in clog free bottles. There are three sealing points within the cap, including a steel pin to help keep the tip clear & open. If CA does build up on the tip or cap, just soak it in acetone for little while. These bottles can be refilled and reused many times. For thin and medium, there is a jumbo 8oz refill available to refill the 2oz bottles. You can also buy cheap squeeze bottles at a hobby/craft shop to use.