Why? Like Weight Watchers...Because, It works! Do we really need to know why or how it works to use the two together?
This question may be one of the most asked questions about finishing a pen with CA. A search of the forum with your exact question will get you a long winter's night of reading.
Here is an answer I was given once...yes, I was curious.
The answer is from:
Dr. Henk J.M. Verhaar, Principal
ENVIRON Home - ENVIRON Global
Willem Arntszlaan
the Netherlands
Q: Does anyone understand how Boiled Linseed Oil and CA glue react to make such a nice finish?
A: Yes. The CA acts as a crosslinker for the BLO - you basically get an
accellerated linseed oil resin matrix with added durability and water
resistance.
(Normally, oxygen generates radicals in the oil which then act as crosslinkers - a much slower reaction, and resulting in a resin with other properties than a CA-crosslinked BLO resin).
BLO by itself cures through exposure to oxygen. Oxygen from the air will oxidize the double bonds in the fatty acid chains of the BLO triglycerides (and remember, all vegetable oils and animal fats consist of triglycerides). These oxidized triglycerides will then attack further double bonds, and attach to them, so that you get a (3D) network of triglyceride molecules. Basically what you get when BLO cures is a natural resin (plastic if
you like). BLO, in contrast to raw linseed oil, contains catalysts (called a
siccatif, usually consisting of heavy metal salts) that considerably speed up the process. BLO cures in hours to days, whereas raw linseed oil needs weeks to months to cure. However, when combining BLO (or raw linseed oil) with CA, a reaction will take place between the CA and the double bonds of the fatty acids. In effect you get a co-polymer resin of CA
and BLO molecules. Since CA is so reactive, this process is much more rapid than BLO curing. The BLO itself is, ideally, completely 'consumed' by the (excess) CA, so no actual normal BLO curing will take place.
The advantage of CA-BLO over straight CA is that you get a more flexible, less brittle resin than with polymeric CA alone.
Back to my personal comments: I am one of the users of CA ahd boiled linseed oil together and I really like the finish I get. No, I don't understand the above answer but Henk does know his stuff. I can go with or without boiled linseed oil but I like the finish better using it.
If interested, my process is outlined in an article at the link in my signature.
Do a good turn daily!
Don
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