Replies

1. 
   SteveSchoene | Jan 22, 2007 02:33am | #1

   Unless you are spraying some particular finishes, such as conversion varnish, there is never any need for any specific product called a sealer.  In general the material you use as a top coat will work perfectly well as the first, or sealer coat.  There are some exceptions, such as when a "wash coat" of a very thin finish--often shellac because it dries so fast and is widely compatible with other materials--that serves to reduce and even penetration of dye or stain.  These are sometimes called "conditioners".  Sometimes a dye may need a barrier coat of shellac to keep it from bleeding into a waterborne top coat. 

   Sometimes in production work a "sanding sealer" is used to speed the process, albeit at the expense of having a somewhat weaker finish system.  These sanding sealers are particularly tricky.  Because they contain additives to make them easier to sand there can be compatibilty issues if the sanding sealer and top coat are not well mated.  This is a situation where brands matter, and where the manufacturer's instructions must be consulted and followed.