Spray Finishing

I will disagree with one point Mike made regarding tips and needles. Matching the correct tip to the viscosity of the fluid being sprayed is crucial to proper atomization. Can you play around with the settings and get it to work? Yes sometimes, but I can attest to the fact that I have gotten more frustrated with finishes when I havent had the correct tip for the viscosity of my material and it either doesnt flow or it sputters.

You might try doing it the other way around...match the viscosity to the gun/set up. I find that if I have to thin the mix, it may be thinner but might flow better. What's the downside...thinner applications. I have no problems with having to put on an extra coat or two. They do come out better.

I try to take advantage of all the adjustments the gun has to offer. This includes experimenting with air pressure, air/fluid mix, pattern, distance from the subject, speed of movement passes, overlap amounts, and one important plus is to have lot of light so you can see the "wet line".



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You might try doing it the other way around...match the viscosity to the gun/set up. I find that if I have to thin the mix, it may be thinner but might flow better. What's the downside...thinner applications. I have no problems with having to put on an extra coat or two. They do come out better.

I try to take advantage of all the adjustments the gun has to offer. This includes experimenting with air pressure, air/fluid mix, pattern, distance from the subject, speed of movement passes, overlap amounts, and one important plus is to have lot of light so you can see the "wet line".



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I do try to keep my coats somewhat on the thin side, more so on the vertical applications. I tend to spray a very light coat all the way around and hit it once more, wait for it to dry then light sand and repeat. I seem to have the best luck with not getting runs that way but still get good coverage.
Other than that I try not to spray thicker coatings or have to get into thinning product. I am spraying anything from DNA and transtint to shellac to waterborne urethane or "lacquers" which is about as thick of a product that I go with.
If I need to spray anything that is too thick for my gun like latex paint I go to my airless. I had a bad run with waterbase satin impervo thinning it to get it to spray through my turbine driven hvlp set. That job cost me alot in time and frustration both mine and the builders. I never went back to satin impervo or any paint for cabinets for that matter and the turbine is sitting in my trailer covered in dust. The only reason I didnt chuck it in the trash was that it cost me 200 bucks and I figured I may find a use for it someday...
Now instead of using paint when a customer requests a sherwin williams or ben moore color I just get it matched by my supplier and use the wb urethane. I get much better results and can have a finish that is hard enough to handle in one day without leaving fingerprints or sticking to itself..

Getting back to what you said though. I will have to give my set ups another look and try playing around with them to see what else I can accomplish with them.:)
 
I do try to keep my coats somewhat on the thin side, more so on the vertical applications. I tend to spray a very light coat all the way around and hit it once more, wait for it to dry then light sand and repeat. I seem to have the best luck with not getting runs that way but still get good coverage.
Other than that I try not to spray thicker coatings or have to get into thinning product. I am spraying anything from DNA and transtint to shellac to waterborne urethane or "lacquers" which is about as thick of a product that I go with.
If I need to spray anything that is too thick for my gun like latex paint I go to my airless. I had a bad run with waterbase satin impervo thinning it to get it to spray through my turbine driven hvlp set. That job cost me alot in time and frustration both mine and the builders. I never went back to satin impervo or any paint for cabinets for that matter and the turbine is sitting in my trailer covered in dust. The only reason I didnt chuck it in the trash was that it cost me 200 bucks and I figured I may find a use for it someday...
Now instead of using paint when a customer requests a sherwin williams or ben moore color I just get it matched by my supplier and use the wb urethane. I get much better results and can have a finish that is hard enough to handle in one day without leaving fingerprints or sticking to itself..

Getting back to what you said though. I will have to give my set ups another look and try playing around with them to see what else I can accomplish with them.:)

This post has the Hawk written all over it. The only real difference is I match all colors to Mag-Na-Max lacquer unless it's off white or white then I adjust the tone and will use undercoater white mostly.
 
Some finishes need intermediary applications that create a final finish.

Here is the loaded gun Mike. Without wanting to be a 2 year old, the question comes down to which finishes and why? So i put a stain on wood to change its color and make it even in color across its surface. Why can i not hit it with a clearcoat and be done.? When and why does one need to put intermediary coatings on. Whats the purpose? I could think up reasons in a production type environment where say cost of coating becomes and issue and hence absorbtion. But why does a hobbiest want to do this.


A basic finish could be just a clear topcoat, comprised of a film finish, like any clear coatings. A stain can be used, primarily to change the color, and/or to enhance the look. Doing this, I would recommend doing samples, as either bare wood, or stained (or dyed for that matter) will look different once an application of anything is applied.

Some finishes, like an oiled finish may not be compatible with the topcoat to be used. In cases like that, a dewaxed shellac application acts like a barrier coat.

Here you hit a point that i just cannot get into my head. Not acting dumb either. I know what shellac is made of. I get the various color variations that can affect the color of the final finish. But what the heck is so special about this stuff that its used as an intermediatory coating or sealer. We disolve it with a solvent. Yet apply it to cover and oil finish. This dont make sense to me. Solvent disolves oil. So does the shellac now blend with the oil. I am presuming we put the oil on like in the case of blo to bring out the grain. So why could one not just wack lacquer over it and be done.


But, once you start experimenting with stains, oils, and topcoats, you'll find that once an application has dried/cured, most topcoats can be used.
This is another loaded gun i would like to discuss. I make a box i sand it. I spray it with lacquer it dries. 2 hours later i can hit it again and repeat sequence and then i am done. So ok i need to get uniformity on my wood finish lets say. So i use a solvent based stain and let it dry and then hit it with lacquer. Ok i am a hobbyist. My work dont count.

But now we have guys that are lets say semi pro. If they get carried away with all the do da day of the various coats etc and the time between applying them etc. This affects production. 1) Dust cannot me made while finishing. 2) That means downtime for the whole shop unless. I am thinking here of a one man shop. SO unless the guy has his own finishing room and even if he has my question when i read Fine Woodworking and see the performance some guys put into the finishing is does the customer even know or care. What is fit for purpose. How much is just getting carried away for marginal benefit. Maybe i am missing something completely here. Few guys love finishing. I certainly did not until i discovered wipe on poly. Now with lacquer well its another world.

So next is to try staining and then final coat. But when to choose what is still the question? and why? If its a matter of whats on hand or availbility yeah i can understand some of what i have seen.


The trick is not to get runs. Spraying an oil base topcoat is more than difficult. I try not to use that method. Making a wiping version is a very fail safe method for application. I can understand this one for sure.



Spraying lacquer can be a problem with humidity. In many cases adding retarder will allow the moisture to flash off. In heavy humidity, the atomized spray will trap moisture in the air and take it to the subject. If it's bad enough, you can see the spray turning white while it's on its way to ruining your day. Did not know this.:( So you saying if its raining or misty outside and i spray on my porch its likely i will have this effect?



That's why it's good to know what you're working with. As we can see, manufacturers can call their product anything they want to in order to sell it. This is a huge issue to me in all sorts of products.



Horsepower is not the critical factor in figuring a spray system. What you need to calculate is CFM's. It's also not in PSI's, as most finishes with a common siphon cup and gun only need about 50PSI-60PSI. It's their CFM (cubic feet per minute) that's a critical factor. A small pancake compressor is great for small projedcts, like shooting brads and staples, as there are just short bursts, and there is usually recovery time for it to catch up. Some spraying or air tool use requires high CFM, over longer periods.

My reference to horsepower was just as an example of the bs one gets from the marketing guys. I understand the whole CFM thing. The issue to me is IF, lets just for argument sake say i was prepared to run that pancake to death do us part, if there was a pressure pot ahead of it for it to fill then could i use a bigger gun. I would get a couple of sprays and then probably have to stop while the tank filled up right?

BUt the point is i could spray. I may not enjoy the job of spraying, i may find it frustrating, i may get very mad at the noise of the pancake



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Here is the loaded gun Mike. Without wanting to be a 2 year old, the question comes down to which finishes and why? So i put a stain on wood to change its color and make it even in color across its surface. Why can i not hit it with a clearcoat and be done.? When and why does one need to put intermediary coatings on. Whats the purpose? I could think up reasons in a production type environment where say cost of coating becomes and issue and hence absorbtion. But why does a hobbiest want to do this.

The hobbyist doesn't have to do that. Keep in mind, a lot of "info" on forums may not be as thorough as possible. It's like the rumor game. You have a line of people, and the first tells the second something, and by the time the last person gets it...it's totally changed.

Ordinarily you can stain or dye the bare wood, and when dry topcoat it with most any finish. Using shellac as a barrier coat would be necessary if you have an incompatible situation. As an example... you have sappy or oily wood that needs to be sealed. Shellac makes a good sealer, but IMO not a durable base for a film finish. I like to use similar chemistry like a lacquer sanding sealer, and then lacquer. For a WB poly, I just use the topcoat.

Here you hit a point that i just cannot get into my head. Not acting dumb either. I know what shellac is made of. I get the various color variations that can affect the color of the final finish. But what the heck is so special about this stuff that its used as an intermediatory coating or sealer. We disolve it with a solvent. Yet apply it to cover and oil finish. This dont make sense to me. Solvent disolves oil. So does the shellac now blend with the oil. I am presuming we put the oil on like in the case of blo to bring out the grain. So why could one not just wack lacquer over it and be done.

Once the oil is dry, you can do that.

But now we have guys that are lets say semi pro. If they get carried away with all the do da day of the various coats etc and the time between applying them etc. This affects production. 1) Dust cannot me made while finishing. 2) That means downtime for the whole shop unless. I am thinking here of a one man shop. SO unless the guy has his own finishing room and even if he has my question when i read Fine Woodworking and see the performance some guys put into the finishing is does the customer even know or care. What is fit for purpose. How much is just getting carried away for marginal benefit. Maybe i am missing something completely here. Few guys love finishing. I certainly did not until i discovered wipe on poly. Now with lacquer well its another world.

Finishing should be done in a separate area if possible. Dust stays airborne quite a while.

So next is to try staining and then final coat. But when to choose what is still the question? and why? If its a matter of whats on hand or availbility yeah i can understand some of what i have seen.

I use maintenance free finishes, primarily WB polyurethane.

Spraying lacquer can be a problem with humidity. In many cases adding retarder will allow the moisture to flash off. In heavy humidity, the atomized spray will trap moisture in the air and take it to the subject. If it's bad enough, you can see the spray turning white while it's on its way to ruining your day.

Did not know this. So you saying if its raining or misty outside and i spray on my porch its likely i will have this effect?

Yes.

Horsepower is not the critical factor in figuring a spray system. What you need to calculate is CFM's. It's also not in PSI's, as most finishes with a common siphon cup and gun only need about 50PSI-60PSI. It's their CFM (cubic feet per minute) that's a critical factor. A small pancake compressor is great for small projedcts, like shooting brads and staples, as there are just short bursts, and there is usually recovery time for it to catch up. Some spraying or air tool use requires high CFM, over longer periods.

My reference to horsepower was just as an example of the bs one gets from the marketing guys. I understand the whole CFM thing. The issue to me is IF, lets just for argument sake say i was prepared to run that pancake to death do us part, if there was a pressure pot ahead of it for it to fill then could i use a bigger gun. I would get a couple of sprays and then probably have to stop while the tank filled up right?

It doesn't matter what's in front of the compressor. It still has to support the pressure pot, and the gun.



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