Messages

Subject:
Re: space bags..
Response To:
space bags.. ()

William Duffield
I am not a chemist, and I don't play one on TV. So, I probably have some details wrong. There are lots of chemicals that are called varnishes. The definition is now much narrower than it used to be. In general, varnishes are finishes made from long chain organic molecules that cure by cross linking. Polyurethane is a petrochemical that cross links. Other natural oils, and chemicals made from these oils, also cross link. Poyurethane evidently does this much better than others, and almost all it cross-linking or bonding sites link up to others during the curing process. This property makes it particularly tough and impermeable to physical and chemical attack. These are advantages. However, if you apply another coat, there are almost no cross-link sites available in the original coat to hook up with the new coat. This allows the new coat, even after it has cured to peel off from the previous coat. Other varnishes leave ore cross-link sites available to hook to the new coats, and therefore are more repairable. The holes in our understanding are due to the finish manufacturers hiding the actual varnishes (and other chemicals) they put in their products. So it is to a large extent, personal experiences or even lore that informs us of the different properties of the finishes we use. A lot of people like polyurethane, in spite of its disadvantages. A lot of people prefer WaterLox, in spite of its disavantages. A lot of people use BLO, in spite of… Others prefer finishes that are not loosely classified as varnishes, e.g., shellac, lacquer, acrylics, latex, epoxies, etc. If I've got some (or all) of this wrong, I'm sure Bill will be able to fix it.

© 1998 - 2017 by Ellis Walentine. All rights reserved.
No parts of this web site may be reproduced in any form or by
any means without the written permission of the publisher.

WOODCENTRAL, P.O. BOX 493, SPRINGTOWN, PA 18081