Treating with Timbor-considerations
Bill Tindall, E.Tn.
The walnut described earlier was treated with Timbor. This material perked my curiosity which led to some literature search on wood treatment and boron chemistry. I also set the bar on frugal and I wanted to know if there are less costly means to this end of insect and fungus treatment. This product from Amazon struck me as a hugely expensive source of boron.
Summary of what I learned
It is has been found that any form of boron is effective as an insecticide and fungicide. Three boron compounds are readily available- boric acid, borax and the Timbor ingredient sodium octaborate. No matter what is applied to the wood, at the pH of the wood what is left on the wood will be boric acid. Hence, the only considerations for treatment choice are solubility, and cost per pound of active boron.
The octaborate (Timbor) is 20% boron and has the greatest solubility in water. It is therefore the best choice if price and availability are not a factor. This same chemical is used as an agriculture boron supplement and may be available much cheaper from ag supply sources.
Borax can be cheaply bought in the detergent section of a grocery in 4 pound boxes. It contains 11% boron. It is sufficiently soluble in hot water for treatment but less so in cold water. I painted, frugally, my ash crotch wood with a 15% solution of borax in hot water.
Boric acid is more soluble than borax and it contains 17% boron. It is available from many sources.