I’m just a carpenter looking to finish some of my own work in my house. My latest project was building a mantel for the fireplace which I did a pretty good job on….finishing it on the other hand has left a little to be desired.
I recently bought a Wagner HVLP Conversion gun and had some real good success spraying some closet doors for the house…I know, level of difficulty is pretty low.
My next job was to spray the mantel I had just built. I wasn’t as happy with that end result. The paint flowed on nicely and really looks pretty good, it’s just not real smooth. The wood is poplar and was super smooth prior to spraying it…
Any tips? I’m not sure my settings for the gun but I believe I had 60psi off the compressor and 25psi setting on the gun. Maybe those settings are too high? Maybe the paint is too thick, I did not thin it. It’s Dutch Boy paint and the can does not recommend thinning.
I need to spray it again to attempt to get a more smooth finish…I don’t like it the way it sits. Is it ok to sand with 150 grit sandpaper and then respray?
I appreciate an constructive comments…
T
Replies
Are you spraying a water base finish?
I've found that, for a smooth finish, you need to dampen the wood after the final sanding, probably 220g, to raise the grain, then sand again with 220 to get the little raised grain nibs off. Don't sand too much, or you'll get past where you've raised the grain.
Then, when you apply your WB finish, it won't raise the grain, and will be much smoother.
Its not a bad idea to do it with solvent base finishes, either.
Yeah, I'm spraying a latex semi-gloss. Is that what the roughness is from the grain coming up through the paint? I'm really a novice at spraying and was not sure what the roughness was from...I really haven't noticed it from stuff I've brushed before.Can I sand the paint I just put down and then respray? And if that's not a problem, is 150 grit good enough or would you suggest 220 for that as well. I was thinking 220 would gum up awful quick from the paint....geez, so many novice questions. And would a palm sander or 1/3 sheet be ok for that or best to do it by hand?Thanks for the tips.
If your surface is rough it may be the result of shooting a "dry coat". IOW, you aren't getting enough paint on the surface to reach "flow out" (the point where there are enough individual particles applied such that they can merge together and become one liquid sheet of material). If you fall short of flow-out, the surface will resemble sandpaper-like grit.
How far are you holding the gun from the surface? If you're too far away the particles can dry before they hit the surface and consequently you'll never achieve flow-out that way, either.
25psi isn't HVLP, IMO. 12 max. Even though the conversion gun you have is HVLP capable, you'll have to adjust the input to acquire HVLP output.
Yes, there's definitely a learning curve to shooting HVLP.
Thanks for the advice HootOwl...I'll sand it down some tomorrow and dial the psi way down to 12 or less as you suggest (as you mention 12 psi I seem to recall someone mentioning 6-8 psi was all they needed - it seems I was out of the ballpark with 25). I'll also get more paint on the mantel to reach "flow out". I wouldn't call the finish sandpaper, but in some areas it's not far from it. In other areas it seems to be pretty good.Learning curve for sure, I knew there would be. Part of my problem is my knee-jerk reaction to spray guns is to think fast. I think I need to slow down with this sprayer as it is a detail or finish sprayer not a production type or wall rig.I really appreciate the advice and suggestions from all...happy to hear any other tips or suggestions too.Thanks.
I agree with the other posts suggesting the cover stain primer (oil) because of it's fast dry time and easy sanding.
We also sometimes use Cabot Problem Solver primer with great results.
I would suggest using a better topcoat though: something like Benjamin Moore, Sherwin Williams, Devoe has much better "flow" characteristics and can be applied heavier producing a better final finish.
As someone else noted make sure that you are spraying enough paint to prevent dry spraying, this will cause a poor rough finish that needs to be sanded out completely before applying the next coat.
Cabot's Problem Solver Primer is for exterior use (only) so far as I know.
Jeff
The Cabot Problem Solver primer is exterior rated primer but we use it quite a bit on windows and trim as well. It penetrates better than just about any other primer (except for maybe Sherwin Williams A100) and covers completely in one coat. This stuff will adhere to just about any surface.
It's a great product.
But the tech data does state:Cabot Problem-Solver Primer may not fully prevent all extractive bleeding in woods with unusually high moisture and tannic acid levels. Not recommended for incense cedar. Knots should be sealed with a high quality knot sealer. Do not use adjacent to fresh stucco. Do not thin this product.
Not intended for interior surfaces. For exterior use only.
(emphasis theirs, not mine)
Jeff
Probably because it contains mold inhibitors that can give off vapors if left exposed.
If you use a 100% acrylic paint it will sand much easier. For taking down the rough spots I'd think 320 or even 400 would work much much better. Again, clogging is much worse on the sandpaper unless you use a paint that is more sandable.
Beer was created so carpenters wouldn't rule the world.
What did you prime it with? The Zinsser shellac based primer works well and dries really fast. That way, you can spray the primer on, sand it smooth and shoot the finish coat(s) in one day. The grain won't raise and you get the smooth finish you want.
If it was smooth when it went on, the grain raised. Poplar gets kind of furry at times but if it's primed first, it's beautiful to work with.
I missed your post while I was replying to the first one.Yeah, I used some Zinsser product but not sure of the exact type at the moment. It did dry fast and I was spraying about an hour after I primed. It seems like it must be the grain I feel. After I primed it was still smooth, it wasn't until after I sprayed the latex that it got kind of rough.Thanks for the thoughts.
Did you filter the paint, or was there any airborne dust in the area? Some of that stuff won't show up until the paint dries. With some paints, you'll get "fisheyes" and with water based, you get little bumps.
"I cut this piece four times and it's still too short."
I didn't filter the paint, I just figured right out of a new can it'd be clean...bad assumption?Airborne dust is a strong possibility...I won't be able to avoid that too much painting in my garage. It is the best space I have available.
Dry coat is a possibility but if it looked really smooth, I'm not sure that's the problem. I would try it with strained paint, and to keep the dust down, hose the floor down and make sure the air is as still as possible in the space where the paint will be sprayed. If tools, shelves, etc have dust on them, use a blow gun and the highest volume fan to get the dust out and off before spraying. If you can rig up a spray booth with light framing and plastic sheeting, that may help. A folding, portable booth should be pretty easy to make if you don't usually paint extremely large pieces.
"I cut this piece four times and it's still too short."
A couple of things...
Cut the paint with Floetrol - it really helps get a smooth finish.
Prime the wood, then sand with 220. Lightly sand again after the first coat.
Thanks for all the thoughts and suggestions.Today I'll lightly sand it down with 220 and try a combination of all these suggestions. I know I can do better. The Floetrol was something I was going to look at before I sprayed but being a rookie it slipped my mind.It'll be a few hours before I can make some noise here around the house but I'll drop back a little later with my results.Thanks again for the help.
Edited 9/3/2007 7:38 am ET by TFri
I never use Floetrol execpt for brushing. Just good old distilled water. Two coats primer, first one sanded with 220, the other for "tooth" to hold the finish on vertical surfaces. You can use a 320 ScotchBrite pad for knocking off nibs between coats.
Best of luck!
Well......I sanded down the sags to what I thought was satisfactory... I resprayed the sanded areas and it looked great until it dried and now I can see my lousy sanding job. Paint is nice and smooth but you can pretty clearly see that I did a bad job of sanding. Might have to whip the orbital out and sand a bit bigger area than just the sag spot. Looks like I'm opening a can of worms.By time I get it right this mantel is going to have 5 coats of paint on it...sheesh.
Edited 9/4/2007 8:08 pm ET by TFri
I learned a long time ago that it's a lot better to shave off runs,sags and nibs and ridges with a frequently sharpened scraper than to use sandpaper. I'm talking about a flat blade about 3" x 6" flat piece of steel that I call a draw scraper but I'm not sure what the rest of the world calls it because I make them myself from old hand saw blades. They save sandpaper and cut the time of in between coat sanding. I've ground many curves,convex and concave to manage moldings etc. Also they only remove the high spots and they do it in one or two swipes instead of endless sanding, and they do it before the material is dry enough to sand.
I'd have to say that spraying is a seat of the pants type of operation. You might have got too much info in one lump to digest it. I would suggest that with a flashlight or bulb in one hand and the spray gun in the other you can find the point of perfection that will still look dry to you but will get wet before it really dries. When you can hit that stage you won't get any more runs. ----The best of--oh well, LOL
Your 3" by 6" scraper is commonly called a "card scraper" here in SoCal. It's a steel card you sharpen/burnish and then use for scraping. Wonderful tool when sharp, very compact, controllable, and powerful. Ideal for leveling gummy stuff.
Yes, You got it right and you descrbed it a lot better than I did. It saves a lot of time waiting to dry and saves a lot of sandpaper too.
I did actually scrape the run with a blade so I didn't have that much to sand, I just didn't do as good a job of sanding as I should have. Live and learn...Not sure what you mean by 'seat of the pants operation'? As far as lighting goes I had two 500w lamps going while I was working and a third to use by hand if needed...the couple areas in question just didn't sag until a short time after I finished spraying.All in all this turned out really well. It's only the second piece I've ever used a sprayer on. The problem is not that I can't make it right, the thing is I just can't do it right on the first try like most folks who are pro painters or at least have considerable experience with HVLP.I'll get it right...just takes a little more effort that it would for some.
"Seat of the pants" is my term for descrbing how you should do it. It only means that you probably can't control everything to do it by the book so you have to change right on the spot to control it right. For instance the temp could mean a lot and so could the humidity etc. So could thinning or changing brands. But you are doing fine if you ask me and I've never seen a pro who didn't mess up now and then. The next thing is to have the capability to fix it.
Floetrol will help a lot, no matter the method of application.
Well, I added about 4oz of Floetrol to a quart of paint, sanded, dialed my psi down to 10, hung three tarps from the ceiling of my garage to make a nice little 10'x10' spray room, and shot the mantel again...it turned out real nice this time.
...except for the two areas I have a little bit of sagging going on. So I'll have to sand them down after it dries a bit (tomorrow night after work) and reshoot them.
Other than that, at this time at least (couple hours after spraying), I think it turned out pretty nice. I also noticed with that sprayer I seem to get a little more uniform coverage from the circle pattern rather than either the horizontal or vertical pattern...so I went with the circle spray.
Thanks for the tips...
T,
Glad to hear you had a better time today. Sounds like you did pretty well.
Shooting HVLP requires that you have the viscosity of the material tuned in pretty dang tight. You can't "cheat" like you can when shooting high pressure by dialing the pressure higher to accomodate a slightly thicker viscosity. With HVLP application, if it's even a little too thick, you'll have trouble getting it to bust up into fine particles. Will likely shoot large spatter gobs instead. Or if it's just a tad thicker yet, it won't feed at all. Getting the viscosity of the material tuned in just right is just part of the HVLP learning curve. What viscosity will work right with any particular material will depend upon whether you're shooting at 4, 6, 8, 10 or 12 psi.
Heavy materials like latex paint are some of the most challenging to shoot properly at HVLP pressures. Good luck at anything lower than 6 psi.....which would equate to a three-stage HVLP turbine gun. This is the lowest psi that I'd attempt to shoot latex paint with. Lower than that and you'd have to thin the material so much that it'll likely have runs on vertical surfaces by the time you achieve flow-out. Don't think you aren't doing things properly if you end up shooting latex paint at 8 or 10 psi. You'll still get excellent transfer to the surface and very little wasted material.....and that's what HVLP is all about.
Lighter weight materials like lacquer,varnish , shellac, etc will shoot very nicely at the lower pressures.
HVLP is also more persnickety about having the right nozzle on the gun.....particularly when shooting heavier materials like latex paint. There will likely be several nozzles available from the manufacturer for your gun. Nozzles designed for the lighter materials won't be able to bust up latex into the small size of particle you're really desiring without over-thinnning a bit. If you do that, you increase the risk getting runs on vertical surfaces as you reach flow-out.
If you find that the round pattern worked better than a fan setting, then it's likely that either your material should have been a bit thinner ........or that you didn't have the "proper" nozzle for shooting latex...or that you weren't feeding enough material to the head. In order to fill out a fan pattern (of width X) you need more material than required to fill out an average round pattern. This means you have to open up the material adjustment a bit more. However, if the material isn't at a thin enough viscosity, then opening the material adjustment screw more may not produce more or enough material to the nozzle.
When shooting a fan pattern in HVLP mode, you'll find that the distance from the gun tip to surface will be about half or less of what you'd have if shooting high-pressure in order to get good/efficient material transfer to the surface.
Don't forget that when shooting a fan pattern you should allow for approx. 50% overlap on the passes. Adjust your application rate/speed accordingly so that the overlapping pass is the one that achieves flow-out of the material.
Edited 9/3/2007 9:13 pm ET by HootOwl
Edited 9/3/2007 9:24 pm ET by HootOwl