Poly Spray Question

[dlrion]

I have recently been using Glossy Polyethylene from a spray can to finish several projects. I think it works like a champ. I am really impatient with the finishing step of the wood process, and this seems to be a great way to do it semi-painlessly.

My question is this, I have a gallon of Glossy polyurethane sitting on the shelf... What do I have to do to spray that onto a project out of my air paint sprayer? I have two, a small detail can, and a larger, cover lots of area one. Would I have to thin the poly down a bit?

Can I leave it in the sprayer? Or would I have to clean it every time? If this is the case, I would rather simply go buy spray paint cans. It seems like I might be able to get away with leaving it for a couple of weeks... the store spray can's get left, and they work without cleaning every time

Thanks in advance,

Dan

 

[FredP]

yes you have to clean the gun every time and you also will need to thin the poly to get a consistency that will spray. what works in one sprayer may not work in another.

 

[Howard Acheson]

Your first question you can answer yourself. Get some cardboard boxes and try out your finishes with various degrees of thinning. Also important is to use the correct sized nozzle and needle. Remember, spraying oil based finishes is problematic. Because oil based finishes dry so slowly, the over-spray is liquid droplets. The over-spray will settle on any surface in the area creating a sort of crust. It's impossible to remove. The only way to spray oil based finishes is to use a spray booth or work outside.

As always, learn and test your complete finishing plans on scrap material before you commit to your project. Don't let your project be your learning curve.

 

[Gofor]

Dan. I haven't sprayed much in the last 5 years, but did a lot of it in the 40 before that. Most of it was "little stuff" like B-52s, F-4s, F-15s and F-22s, but should be able to help you set up your guns, show you how to clean and maintain them, and give you a few pointers on getting the viscosity and pattern right.

Problem right now is that neither of us has a decent place to spray inside, and the weather is getting a bit cold for outside. Anything below 60 degrees will be really pushing it for a novice sprayer, even if we can move the item into the heat after spraying so that it will cure correctly. May want to wait until spring. Your shop in the winter is definitely not a safe place to crank up a spray gun of any size, and neither is mine.

And the answer to your question is that yes, you definitely have to thoroughly clean the gun after each use, and you have to do it before the coating sets up. Not something you can leave for the next day.

I would also add to Howard's excellent advice that the dried overspray is also highly flammable, as the dried droplets have a lot of surface area that lets much more oxygen feed the fire. Kind of like steel: A steel sheet or rod won't burn, but steel wool, which has a lot of surface area exposed to the air, will, and can even self-ignite if you put an oxidizer like acid on it. It doesn't take much of a spark to get over-spray going.

Go

 

[jhreed]

Mark, does that mean that when I am spray painting in the garage I have to move my wife's car out?

 

[Gofor]

Mark, does that mean that when I am spray painting in the garage I have to move my wife's car out?

James: Not really. I'm sure she'd be happy with a new one :rolf:

Car in your garage::rotflm::rotflm:. That's about as likely to happen as one finding a way to squeeze into mine!!

My personal opinion is that its a shame to waste all the research and engineering money spent by the manufacturers to make vehicles leak proof and corrosion resistant by keeping them sheltered. That's my story and I'm stickin' to it.

Go

 

[dlrion]

Mark,

I would love to learn about painting, I think you are right though. I do need some place to do it. I have been thinking about making a lean too "paint shed" but then it would have to be both heated and ventilated.... which is a tricky propasition with a small area.


Maybe I should just wait until summer.

Dan

 

[erasmussen]

You might just have to use wipe on poly until summer, or invest in a nice new shop

 

[pslamp32]

I don't use any oil based finishes anymore since I discovered how much I like shellac and waterbourne lacquer. Like most, I used a lot of minwax poly before. I always liked my results when I thinned it with about an equal amount of mineral spirits and applied with a rag, sponge or brush.

 

[Gofor]

Mark,

I would love to learn about painting, I think you are right though. I do need some place to do it. I have been thinking about making a lean too "paint shed" but then it would have to be both heated and ventilated.... which is a tricky propasition with a small area.


Maybe I should just wait until summer.

Dan

Making an impromptu spray booth for use during warm weather is not too complicated or expensive. A good organic respirator is all that will be needed for the limited spraying that most furniture items require. One of the full face hoods that blows filtered air over your face is even better. Clear plastic sheeting makes cheap disposable walls to contain overspray and give you dust control, as long as you have a roof and a framework. A turntable to put the items on when spraying is a definite bonus.

Problem in the winter is heating the air without without adding an ignition source. That complicates things exponentially.

I am oversimplifying it here, by a long shot, as there are more safety and quality issues, but suffice it to say that once the weather warms up, I can get you familiar with the equipment and process, outside, with no more equipment investment, and then you can decide how far you want to go with it. Having a spray capability, even if it is small, will open your options as far as tinting and dyes as opposed to stains, and coating choices to include lacquers and shellacs that are much more easily and efficiently sprayed than other means of application. You have a lot of talent so it would be a shame to limit it because of your coating choices.

Go

 

[BrianInChatham]

I had the exact same dilemna a few years ago- I like the "plasticy" look of gloss poly in some applications, but was making a mantle that was much too large for spray cans to be practical. I thinned down some canned stuff until it seemed to work in my sprayer (a cheap Wagner). It worked fine at first, but after a few moments the spray started to get inconsistent, with larger blobs in the mist resulting in lots of splatter and uneven coverage. No amount of fiddling seemed to resolve this, and the resulting coverage was totally unacceptable (I think much of the problem arose with the cheap equipment I was using). I finally gave up and wiped the project down and started over.

The method that finally worked for me came from and unexpected direction- my mother in law. She suggested using a foam brush (which I have not been a fan of) with slow, even strokes. With a bit of experimenting I was able to get an outstanding result. Pour a small pool of poly on your work surface, and draw it out in a single smooth stroke, don't let the brush get dry. Don't brush back and forth or try to work it into the surface, it'll just get foamy and you'll have to wipe off and start over (ask me how I know..). Overlap subsequent strokes slightly, add more poly as needed, and so on. Don't plan on finishing with a single coat- 2 or 3 thinner coats will give a much better result than one heavy one. I was able to get a near perfect mirror finish this way, and it probably took less time than spray application would have (a lot less prep of your workspace), and certainly cost a lot less.

Don't know if brushing will work for your application, but if so I'd highly recommend giving it a try.

 

[DWSmith]

I learned to spray at the hands of a master in a furniture plant starting when I was 18. Since then I have finished in other furniture plants and cabinet shops as well. If you want good advice about spraying, get the book "Understanding Wood Finishing" by Bob Flexner. It is as good of a basic to advanced book as I have ever seen and it will help tremendously.

 

[pslamp32]

If you want good advice about spraying, get the book "Understanding Wood Finishing" by Bob Flexner. It is as good of a basic to advanced book as I have ever seen and it will help tremendously.

+1. I really do like this one, by far, the best of all that I have...

 

[MrAudio815]

Hey Dan,

Can't help out much, but I do have the book "Understanding Wood Finishing" by Bob Flexner. I can look up anything you'd like and send you a few pages if needed?

But it does look like you are covered with Marks help. He's a amazing guy~!

Matthew

 

[dlrion]

Looks like I book to read this winter. :thumbs_up

Dan