Replies

1. 
   JohnWW | Mar 09, 2004 04:15am | #1

   Water based polyurethanes are usually the finish of choice where you are trying to minimize color change in the wood.  For sun protection, get one meant for outdoor applications.

   Whoever recommended shellac for your application was clueless.

   John W.

2. 
   Gretchen | Mar 09, 2004 02:21pm | #2

   When you say it changes the color a lot you may not be able to control that.  When you put mineral spirits on wood, for example, that is the color you will eventually attain with a clear finish. So you may want to test this.  What you can control is the ambering effect of some finishes such as oil based varnishes.

   Gretchen
3. 
   joinerswork | Mar 09, 2004 05:22pm | #3

   Rob,

   I've had best success with a very light spray application of nitrocellulose lacquer.  You want the first coats to dry as they contact the wood, not penetrate and then dry.  Once you've sealed with several coats misted on from a distance, you can start spraying a bit heavier coat to provide more protection to the surface.

   Regards,

   Ray

1. 
   VeniciaL | Mar 09, 2004 06:29pm | #4

   Lacquer does not penetrate wood. It does not matter how it is applied. It should be sprayed lightly so as not to run, but should not be "misted" from a distance so that it dries as quickly as you describe. This will result in a rough appearance of the first few coats and possible adhesion problems.

   The first several coats need to "wet" the wood (very slightly). Lacquer is a completely evaporative finish. The solvents and diluents completely evaporate, leaving a film of solids only on the surface.

   Nitrocellulose will be water white on initial application, but will eventually (months to years) yellow slightly. CAB-Acrylic (Cellulose Acetate Butyrate) will not yellow.

   VL

1. 
   joinerswork | Mar 10, 2004 05:33am | #5

   Venitia,

   I was describing a technique to achieve the results the poster was asking for- I realise this is not the accepted method for applying a sprayed lacquer finish.. If the lacquer wets the surface, it will darken it as described  re the mineral spirits in a previous post. 

   You are correct in saying that a misted on film will have a rough appearance, less so the finer the atomisation of the mist.But this is alleviated once the surface is sealed by several mist coats, and a heavier, wet coat can be sprayed without wetting thru the previous ones. 

   I'll grant you that adhesion might be better achieved by spraying an initial wet coat, but I think the original post put durability below appearance.

   Regards,

   Ray

1. 
   VeniciaL | Mar 10, 2004 06:37pm | #6

   Sorry Ray,

   What you describe is wrong in theory and in practice. Laquer will "darken" the wood only by the light dispersion properties of the solids film on the surface left after evaporation of the solvent/diluent. That darkening will be minimal - the least of just about any finishing method other than super blond shellac or water-borne finishes. Any slight color intensification caused by the wetting action of the laquer thinner/solvent phase will disappear after the first several coats are hard. A very thin lacquer film does not seal the wood against subsequent thicker lacquer coats. The solvent of the subsequent coats actually completely penetrates the first few coats.

   The mineral spirits "trick" of predicting the darkening of an oil or varnish finish is an accident which relies on the similar appearance of wood wetted with mineral spirits alone and wood with the hardened oil or varnish finish in place. Laquer thinner does not act in a similar way.

   VL

1. 
   joinerswork | Mar 10, 2004 09:31pm | #7

   Venitia,

   Uh...o.k...whatever you say.  Just know this has worked for me.  Your experience is obviously different.

   Regards,

   Ray