Poly Urethane Finishes

[Crash]

Alright you experienced finishers.

I work mainly with ponderosa knotted pine on my chest and craft items. You would be surprised at how many people ask for pine on bookshelves due to the difference in cost compared to oak. So needless to say I have a lot of my customers asking for pine. I use 1x12 shelving board and work it to what is needed. I have always used brushes with my polyurethane finishes. But the other day my dad gave me a brand new sprayer and told me that I would get a better finish and finish quicker using a sprayer. (scary) when you aint never used a sprayer before. I asked him to show me and the consistencys that I needed to mix. He told me to practice and figure it out. Thats the way me and him work. We believe in hands on experience. But I was wondering if someone could give me some pointers please.

This is the process that I currently use on my wooden chest (all sizes).

Sand with 80 grit then 100 grit or 150 then I sand with 220. After that I remove the dust of course and I brush on a 75% poly and 25% Paint Thinner mixture. After this is dried I sand with 220 if I feel it needs it (literally) I feel for roughness and so on on the surface. Then I apply a 100% poly coat on. After that Dries whether I put another coat on it or not depends on how it looks.

Am I doing something wrong here or what. I mean my finishes come out looking good I've not had any complaints but theres always room for improvement.

As far as spraying on my finish coats can somone give me some detailed info like if I dilute the poly what to use and what amounts would help and then how many coats.

Thanks robert and paul for responding on the other forum. I just copied and transferred this discussion today 8-9-10 because it was fairly new and I still would like to have some experienced insight.

[Crash]

Heres the pics of the one that I just finished. This has one base coat of 75 25 % poly & thinner mix. And 1 top coat of 100% poly.

[thewoodwhisperer]

I will also recommend practicing quite a bit before hitting your projects with the sprayer. Rob said it best above, but there is another reason I'll add. Oil-based poly isn't exactly the easiest stuff to spray. Its very easy to get drips and runs and you could also get lots of air bubbles in the finish. Another thing is that the overspray is wet and remains wet after it hits the floor. So this can me messy and dangerous. So make sure you are spraying outside (unless you have a proper booth setup). Get the feel for how the poly lays down and play with the dilutions. Hopefully you'll find something that works for you. I never really did, so I kind of gave up and decided I would only spray quick-drying finishes from now on (shellac, lacquer, and water-based).

[rob45]

Well, your dad said it best- practice and figure it out. Very few things beat experience.

What type of sprayer, and what brand of poly?

How much, if any, you thin the poly depends on if the sprayer can push the product unthinned or not. Also, some of the chemical manufacturers state directly on the can "DO NOT THIN". For years we thought this was an attempt to sell more poly, until I did a few projects that had bad fisheyes in the finish- turned out I was going TOO heavy with the thinner, at least according to the manufacturer.

Generally, I like to dilute slightly (5-10%) on the initial coat to allow better absorbing into the wood, then 100% poly for each successive coat. Just like your process, only I do not like to thin as much if I can get away with it.

If you're new to spraying, your biggest challenge will be deciding how to adjust the gun for each product, and deciding if it needs to be thinned or not.

You did not mention what type of sprayer. If it's an airless unit, no thinning is required (other than to allow better penetration into the wood on that first coat, and the need for that depends upon the wood species utilized). HVLPs really depend upon the capabilities of your particular unit.

Welcome to the world of spraying. It definitely is a whole new ballgame. Obviously setup and cleanup times are longer, but for the most part it is well worth it. Unless your projects are very small, it is indeed quicker. Done properly, two coats with a sprayer are going to feel like you did several coats with a brush.

Use scrap cardboard to dial in the gun first. Typical tan/brown cardboard works best because it allows you to see the spray pattern. This also helps you establish the proper rate of speed (how fast you move the gun).

Practice...If you are consistently spraying the same type of project over and over, you should pick it up very quickly.

BTW, nice chest!

Good Luck,

Rob

[PaulMarcel]

BTW, nice chest!

Are we allowed to say that here?! j/k

Good posting; I definitely agree spraying is faster than a brush just that sometimes I think of the cleanup and well don't spray