Spraying Minwax polyurethane with HVLP

[Scott LeBlanc]

I have been brushing oil based and using gel stains for a while.. I am doing some bigger projects so I recently bought a gun with a 1.4mm tip. I have read elsewhere that thinning urethane with mineral spirits or naptha will make it spray well and leave a good finish. I have no knowledge in this area and would sure like to hear what everyone thinks about it.

[Jim Becker]

The vast majority of us will recommend you do not spray oil-based varnish...it dries so slowly that you're going to have a major mess with any overspray, etc. Spraying is best suited to finishes that dry relatively quickly, such as shellac, NC Lacquer and water borne finishes, such as Target's USL or even Miniwax Polycrylic.

[JC Fetz]

I spray Wood Kote (http://www.woodkote.com (http://www.woodkote.com/)) oil based polyurethane thinned with naptha (approx 10%) and have had excellent results. I haven't had any of the problems previously mentioned. I spray on a warm day and set my stuff in the sun to dry and it can be handled within a couple hrs. Provides a very durable finish.

[Phil Phelps]

I spray Wood Kote (http://www.woodkote.com (http://www.woodkote.com/)) oil based polyurethane thinned with naptha (approx 10%) and have had excellent results. I haven't had any of the problems previously mentioned. I spray on a warm day and set my stuff in the sun to dry and it can be handled within a couple hrs. Provides a very durable finish.

I can't imagine the junk that I would get in my work if I set it in the sun. Your sure your not under a plastic bubble?

[JC Fetz]

Well, I'm just a part time hack with a small garage shop without a spray room or anything so I have to spray outside on calm days. I haven't had any problems with much junk getting into my finish (an occasional small bug) and I've been doing it this way for several years. Calm day is key. Here's the top of a cabinet I made. Razor smooth and no junk!

[Tom Francis]

Personally, unless you have a suitable place to spray a mineral based product, I would stick with lacquer since it dries quickly. That is important for (2) reasons.

Lessens the problem of overspray sticking to everything in the vicinity.
Less time for dust nibs / bugs / etc. getting in your newly sprayed finish.Go to Lowes and buy a can of Deft (lacquer). This sprays well and is a pretty good finish. It is also much easier to rub out the finish with steel wool, and if you ever have to repair the finish, it is better for that as well.

Or, you could go to a paint store and buy a can of precatalized lacquer (Campbell) and that will work well too. IMHO http://www.sawmillcreek.org/images/icons/icon7.gif

I have had excellent results spraying lacquer, and I don't have a booth. I have had to spray my large projects in my backyard. Lacquer doesn't hold up as well for table tops exposed to moisture, but for bookcases or other projects where people are going to be putting wet items on it, it works fine.

[Tom Francis]

Lacquer doesn't hold up as well for table tops exposed to moisture, but for bookcases or other projects where people are going to be putting wet items on it, it works fine.
Correction to the above quote:

It should have been "where people are NOT going to be putting wet items on it, it works fine."

Sorry about that http://www.sawmillcreek.org/images/icons/icon10.gif

[Kevin Barnett]

Personally, unless you have a suitable place to spray a mineral based product, I would stick with lacquer since it dries quickly. That is important for (2) reasons.

Lessens the problem of overspray sticking to everything in the vicinity.
Less time for dust nibs / bugs / etc. getting in your newly sprayed finish.Go to Lowes and buy a can of Deft (lacquer). This sprays well and is a pretty good finish. It is also much easier to rub out the finish with steel wool, and if you ever have to repair the finish, it is better for that as well.

Or, you could go to a paint store and buy a can of precatalized lacquer (Campbell) and that will work well too. IMHO http://www.sawmillcreek.org/images/icons/icon7.gif

I have had excellent results spraying lacquer, and I don't have a booth. I have had to spray my large projects in my backyard. Lacquer doesn't hold up as well for table tops exposed to moisture, but for bookcases or other projects where people are going to be putting wet items on it, it works fine.
Okay, this doesn't really answer the OP's question. I prefer poly myself. I spray outside on calm days and let the item dry inside. If I can recoat before 2 hours, I may not sand depending on smoothness.
Poly has wider availability and better durability. If sanded between coats and not put on shellac, it's hard to mess up. Lacquer, IMO is easier to mess up. Precat is noxious.

[Mike Wilkins]

I have sprayed poly finish many times. My shop is too small to have a dedicated spray booth, so I spray outside on a calm, non-windy day. Even the slightest breeze will deposit gunk and small bugs onto the finish. My method is to thin the poly 50/50 with mineral spirits for the first 1 or 2 coats.
Then after suitable drying time, I spray subsequent coats using a 75% poly/25% mineral spirits blend. Has worked well for many projects. In the winter or on breezy days, brushing is the normal method for me.

[Joe Chritz]

You can spray it but there are so many better options that are a phone call away I don't see why.

There are waterborne urethane finishes designed for spraying, Conversion varnish, arcylics, etc.

Ultimately you are just putting the finish on the piece, since it takes a fairly long time to set it will level out generally pretty well, regardless of how it gets on.

You are missing a lot of options by not branching out.

Even your local sherwin williams store has some great finishes available. The prices are very close to minwax polyurethane. If you are spraying outside anyway, their solvent conversion varnish or cab acrylic are supposed to be very good.

Joe