Replies

1. 
   SteveSchoene | Mar 17, 2009 01:53pm | #1

   The shellac sealer cannot but help on the MDF.  Whether you need the pore filler depends in part on whether you have visible cut edges of the MDF that will drink up sealer at a prodigous rate. 

1. 
   hdgis1 | Mar 17, 2009 02:31pm | #2

   Nice to see you again! Am I missing the boat with these kind of questions...

2. 
   willyx2 | Mar 22, 2009 12:33am | #3

   Had this same questions a few weeks ago, I had great success with the shellac based primer/sealer spray can purchased from hd, (buddy of mine purchased the gallon size at a considerable savings-due to many doors to prime), didnt sand the mdf, light sand with 220 sand between prime coats x3, and the mdf came out like glass-which was my desire.  Coated with waterbased primer from SW sprayed thru my hvlp. good luck

3. 
   YesMaam27577 | Mar 23, 2009 12:07am | #4

   Although I like your plan, I'd be careful to allow the latex to FULLY cure before I put any lacquer on top of it. And although latex dries to the touch in a few hours, it actually takes about a week for it to fully cure.

   Use the very best latex that you can afford. I like Duron's Plasti-Cote. It flows out nicely, and does a fair job at hiding brush and roller marks. I've sprayed it, but it needs lots of thinning (as does just about any latex. (And my sprayer is a compressor-powered HVLP.)

   To help with the smoothness of the sprayed finish, I generally use denatured alcohol as the thinner -- it helps the latex flash over more quickly, avoiding runs and sags.

   The shellac is a good idea. It meets all of the needs you questioned --sealing to prevent swells, and filling the pores.

1. 
   SteveSchoene | Mar 23, 2009 01:04am | #5

   The top coat he proposed is a waterborne, not lacquer.  Lacquer, which is solvent based, has solvents that could damage just about any finish underneath, and is definately not recommended over a waterborne paint even with the month of cure time needed for a full cure. 

   But, of course the term lacquer is used on lots of waterborne finishes.  That's just to say that the manufacturer suggests similar applications as for nitrocellulose lacquer, but really there is very little chemical similarity between solvent lacquer and waterborne lacquer. 

1. 
   Shoemaker1 | Mar 23, 2009 01:18am | #6

   but really there is very little chemical similarity between solvent lacquer and waterborne lacquer. Could you expand on that? I am soon to need that knowledge. Rather hear if from a user, rather web site info.

1. 
   SteveSchoene | Mar 23, 2009 04:06am | #8

   Solvent lacquer uses nitrocellulose resin (often with something else to alter the properties somewhat) the resins dissolve in lacquer thinner.  The lacquer is applied, the solvents in the lacquer thinner evaporate.  The finish has dried, not cured, and will redissolve in lacquer thinner, and when the thinner evaporates again it would form a lacquer film again.  Each new coat dissolves, to some degree, the lower coats, and when the solvent evaporates they will have fused themselves together into what amounts to a single coat. 

   Waterborne "lacquer" is an acyrlic resin finish, that uses water to separate little "packets" of resin and solvent (typically something like ethyl glycol).  The water evaporates, the little packets coalesce and the process completes a curing process. It won't redissolve in water.  Some of the solvents might damage the finish, but not just dissolve it so it could reform when they evaporate.  Some waterborne finishes to have some degree of "cross linking" so that when multiple coats are applied within a short enough time span they link together enough that they don't display "witness" lines, but they still are mostly separate coats. 

   So chemically they have nothing in common--the primary resins are different and so are the primary solvents.  Lacquer dries, waterborne coalesce and then cure. 

2. 
   hdgis1 | Mar 23, 2009 01:53am | #7

   Thanks for tip about waiting to coat paint. I will be using water borne 'lacquer' so it will be interesting to see what steve has to say about the differences between waterborne and regular lacquer.Chris

4. 
   flairwoodworks | Mar 23, 2009 04:16pm | #9

   Chris,

   I don't know if latex would cause MDF to swell, but it's certainly a thought. Unless someone chimes in and says it's a non issue, you're wise to stick with the shellac sealer. Or you could experiment. Regarding the porous edges, spackle works fine.

   Don't quote me on this, but to spray latexes, I believe that you need a narrower tip to properly atomize it. I bought an HVLP about two years ago and had to buy some accessory tips so that I could spray latex should I desire to. Sorry I don't remember any more, but I still haven't tried spraying yet!

   Chris @ www.flairwoodwork.spaces.live.com
   (soon to be www.flairwoodworks.com)

    - Success is not the key to happiness.  Happiness is the key to success.  If you love what you are doing, you will be successful. - Albert Schweitzer

1. 
   Shoemaker1 | Mar 24, 2009 02:18am | #10

   Thanks.
   Does now make sense!!
   I'll be reading the labels of the waterborne real carefully now.

2. 
   hdgis1 | Mar 24, 2009 04:21am | #11

   chris,
   Just purchased the fuji mini-mite 3 and spoke with Paul (president I believe) at said company. He suggested that either the 1.0 or 1.4 mm tip shoudl work fine for latex as long as it is properly thinned.
   chris