Three types of finish (resins)

 

·         Evaporative This is a finish where the solvent evaporates and the finish resins dry.  Examples of this are shellac, lacquer, and wax (when used a a finish).  If you add the solvent back in, it will redissolve the finish.  Flexner calls this "spaghetti."  Spaghetti pasta comes dry, you add water and cook it and it's soft and flexible, and if you let it dry out, it turns hard again.   These finishes are fast drying.

 

·         Reactive These finishes cure by reacting chemically.  Usually this is by absorbing oxygen and forming polymer chains.  Sometimes, there is a thinner that reduces the viscosity and has to evaporate first.  Then the chemical reaction starts.  Examples of this are oils and oil-based varnishes.   Flexner's "Tinkertoys."   Adding the thinner back in does not redissolve the cured finish.   These finishes are usually slow curing and full curing may take weeks or more.

 

·         Coalescent These finishes have large molecules whose edges are softened by a solvent.  The example is water-borne finish.   Glycol ethers soften the edges.  Water is there as a thinner.  Water evaporates, then the molecules get close together and the sticky edges bond.  Then the glycol ethers evaporate and the finish dries.  Flexner's "soccer balls"

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