Replies

1. 
   | Sep 09, 2007 03:36pm | #1

   Weelis,

   Although I usually use shellac as a finish on my furniture, I have sprayed MW polycrylic with my cheapo HVLP system. It goes on great! Remember to use a piece of scrap for getting the settings and technique down. I found that I had to spray fairly wet, almost to the point of running, to get it to flow out smooth and not dry with a rough feel. I would also very lightly scuff sand between coats with something like 600P sanding sponge. Good Luck.

    

   Bob, Tupper Lake, NY

2. 
   isaacvw | Mar 09, 2011 06:44pm | #2

   spraying polycrylic with HVLP

   I have sprayed ploycrylic with a 3M HVLP turbine and gun, and it works fine, with one caveat: your turbine may produce too much pressure.  In my system's case, the HVLP turbine makes around 100 PSI, and in spite of being able to adjust the needle travel, fan pattern, air caps, and fluid tips, the system pushes out WAY too much finish. 

   I called 3M and spoke to Duane in tech.  He recommended adding a ball valve in the air hose, to reduce the PSI at the gun.  This worked well, and allowed me to fine tune the pressure until I had a spray pattern that was manageable, with little overspray. 

   One word of caution: the lower the pressure, the poorer the atomization of the finish.  Use a small fluid tip, an air cap with small holes, and keep the needle travel short.  Otherwise, you'll get splatters instead of spray.

   good luck!

   -isaac

1. 
   CallMeChaz | Jul 01, 2021 02:46pm | #7

   A valve will not reduce "pressure" in a spray system, it reduces air "volume". Use a proper gun-pressure "regulator".

3. 
   SteveSchoene | Mar 09, 2011 08:19pm | #3

   Folks do spray the Polycrillic and if you have a bunch (and it is still fresh) that's the thing to use.  Shop cabinets are great to learn on.  I would suggest that spraying is easier with material designed specifically for spraying.  Polycrylic and similar products most designed to be brushed have been thickened to suit that purpose better.  But Target and General Finish--and plenty of others, make waterborne finishes specifically designed for spraying.  If I I had to buy finish, I'd spring for these finishes that are better suited for spraying. 

   As far as thinning, carefully read the manufacturers technical data sheet or can label.  Most waterborne finishes are pretty significantly limited in how much they can be thinned--usually no more than about 10% water.  Too much thinning and the finish doesn't coalesce properly, making it weak with poor adhesion. 

4. 
   HowardAcheson | Mar 12, 2011 10:31am | #4

   If you are new to spray finsihing I strongly suggest you get Charron's Spray Finishing book.  Amazon will have it.  You don't just fill up the gun and pull the trigger.  The book will tell you how to set up your equipment and how to adjust it for the type of finish you will be using.  It will tell you how to "read" the spray and the resulting finish to know what adjustments you need to make to get the best results.  It will also talk about the various finishes and how to adjust their viscosity.

   Finally, practice on cardboard boxes using water first to learn the techniques on how to spray.  Better to have water blow back into your face when you spray into an inside corner.  Once you've learned with water, do the same thing with finish and learn how to make adjustments to the spray.

   Only when you have learned the lessons should you attempt a real project.

   In our shop, an apprentice finisher would take a week to learn and develop his skills before he would be allowed to do something real.

   Many folks spray Polycrylic.  Don't thin it unless you get instructions from Minwax.  Water is not a thinner for waterborne finishes.  It's a carrier of other chemicals that come together when the water evaporates.  Adding water can cause the finish to not dry properly.

5. 
   musicbymark | Feb 25, 2012 11:32pm | #5

   Spraying Polycrylic

   I'm trying it tonight for first time after seeing a guy w/ a goofy youtube video, and just using my cheap $10 Harbor Freight touch up gun, it's working great. No BRUSH STROKES or BUBBLES!  But the finish is rough... probably due to srapy gun and thickness of finish, and how it doesn't settle as smootly as thinner finishes or ones that dissolve previous layer would. I'll need to rub out the finish to get it shiny I can see, but YES, I would spray again.

1. 
   SteveSchoene | Feb 25, 2012 11:47pm | #6

   Remember that this is a waterborne finish and the first coat WILL raise the grain and leave a rough surface so that the first coat definately will need sanding. 

6. 
   CallMeChaz | Jul 01, 2021 03:10pm | #8

   Over-thinking this. Unless a finish specifically requires thinning per the manufacturer, thinning is the last thing you want to try to get a good spray. If thinning is listed as optional, do not exceed the recommendation--again, only thin as a last resort. If thinning is not listed, you are putting your project in jeopardy if you go more than 5-10%. Over-thinning can destroy the integrity of the product.

   First, experiment with gun pressure, tip size, and product flow to try and get the pattern you want. In general, use the finest tip that will get a proper pattern if you want the smoothest finish. Bumping the pressure up (within reason) will will also atomize finer droplets especially with smaller tips, but will cause more overspray. Polycrylic is not thick, and you may be able to drop to a 1.3 tip with some trial and error. A 1.5 tip with no thinning would be preferable to a small tip and thinning, unless you simply cannot get smooth finish otherwise.
   .
   Polycrylic dries fast, so as one respondent said you have to put it on wet or it won't level out. 600 grit is way too fine between coats, and will not provide the proper tooth for good adhesion of the next coat. Manufacturer recommends 220 grit after 2 hours dry time, which I find more than sufficient for a smooth coat

1. 
   fivebirdscustom | Jul 02, 2021 01:30pm | #9

   Hopefully, the OP has found a solution. This thread is nine years old.

   But, your advice is still good. LOL