Woodfinishers Weblog

Wood finishing forum for professional finishers

I’m new to the Finishing Game and have questions

The following are a few questions sent into me by a new finisher  I am posting with his permission.

Hi Greg

I am new to this spraying game and wondered if you could let me know what flash off means, also I’m using Sayerlack Hydroplus: waterborne clear self-sealer and so far so good, the finish is great, though i am working in a cold barn with a home made spraying booth and even though I have extraction and filters I am finding particles on the finish. Also what is a good grit to sand in between lacquer coats?

Hi Loukas,
Ok, the term “flash off” is the term referring to the solvents evaporating generally used in reference to solvent based coatings but does in fact apply to water based materials, the solvent being water.

There is the first period after you have sprayed something; its wet, and the solvents are evaporating, i.e. its drying. After that point the coating continues to dry but at a much slower rate. That first stage is the time the solvents are “flashing off”. After that point it might be dry to the touch but still soft. In essence the top layer of the coating has dried but the deeper layers are still drying. Most all coatings dry from the top down unless they are epoxies and urethanes that dry internally with a chemical reaction caused by mixing a part A and B.

Water base materials generally dry slower than solvent based materials but will dry even slower in cold or humid conditions. To speed things up you do two things; heat your materials and or heat your spray area. As you are using water base materials you don’t need to worry about having explosion proof heating (which is something you do have to have when spraying solvent based lacquers.) heat and low humidity with air flow will dry your work faster. That it is drying so slowly makes it more susceptible to dust landing in the still wet finish.

You can also heat your lacquer. For one, don’t store it on the cold concrete floor over night. Minimally keep it off the ground. Warm it up before using it by sticking your gallon pail in a tub of hot water. Or wrap a heating blanket around the can. There are more expensive fluid heaters that heat the liquids as they are going through the hoses to the Gun, Those things are for the pro shop that you aren’t going to need for a while (you can look up fluid heaters or pail heaters on sites like Grangers, Northern tools, and Mc Masters-Carr)

 Just getting your water based materials above room temperature is gong to make a significant difference in the flow out and drying time of you work. Cranking it up to about 98 degrees and you’ll see a finish like glass. When you start heating up the materials that much however you need to have the ambient air temperature and the work piece temperature relatively high other wise your hot materials are going to start pulling moisture out of the air and that will cause you finish to have a slightly milky appearance, which in essence is moisture trapped inside the coating.

Ok the next question: what grit sand paper should you use in-between coats, good question. I use 220 silicone carbide paper 220 is the grit you need much higher than that and you are wasting your time. the silicone carbide is a great paper as the tiny little particles that make up the sand in the sand paper break down evenly so you get and even scratch. There are other fancier papers, Abernete and garnet some people thing there the best others don’t. The other thing you can use is a scotch bright pad there are several different brands 3M makes a few and Mirca (another abrasives company makes a few)

Hope that helps, send me some picture of your operation in exchange for the free advice I would love to hear how it all turn out.

I’m going to post these conversations for others to view, if that’s ok with you.

Best of luck,

Greg Saunders

ANNEX PAINT

818-439-9297

 

 

 

November 25, 2009 - Posted by | Finishing failures and the fix, Tips and Tricks, Water based Lacquers

3 Comments »

  1. I’m finnishing a table top that I made from left over madrone hardwood flooring and I want to know how to put on a final smooth varnish. I’m using a paint brush that streaks.

    Comment by Paul Butterfield | July 5, 2010

  2. Hi Paul,

    You are not going to get as good a finsih with a brush, the reason they invented the spary gun was to solve that very problem. I would suggest that you buy an inexpensive but quality spray gun and then rent a compressor and spary the table, It will look a whole lot better when you are done and you will have gained a valuable skill that is not all that hard to learn. After that you find more things to refinnish. Some where else on this blog is good artical on how to use a spray gun, stud that one and then get the spary gun and practice.

    Comment by Greg Saunders | July 7, 2010

  3. to whom it may concern…after doing hours of research on how to apply a glaze finish to cabinets I ran accross your website. I read through all of the material provided here as well as the demos done by Greg Saunders. Not specific to my project I contacted Greg to see if he could help me. Not knowing what to expect I was very pleasantly surprised by the way Greg listened to my questions and was more than willing to explain every aspect of this project. I want to thank Greg for his willingness to share his expertice. I believe he is a true asset to your company! Thank you Greg for all your time and patience.

    Comment by Tom Bodrovics | April 13, 2011


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