Difference between spraying and brushing

[Trace Beard]

I picked up a 4 stage fuji turbine, a siphon gun and a new XPC gravity gun. Now I'm trying to figure out what adjustments I need to make when I make the switch.

Do some products look significantly different when sprayed versus brushed? Does an oil based penetrating stain look the same when sprayed or wiped? Shellac?

Maybe the difference has more to do with the type of wood or how the wood is prepared or maybe once a seal coat has been applied there's not much difference at all.

I have Jeff's spray book and DVD and I think I'll order Bob's book on finishing this week.

Thanks for your input.

Trace

[Scott Holmes]

Trace,

"Does an oil based penetrating stain look the same when sprayed or wiped?"

Oil based stains are not really made to be sprayed... I suspect the pigment will clog small tips. Also the stains are made to color the wood with pigment that is held in place with a binder. The binder can't usually hold a thick film of stain so wiping will still be needed. Spraying water oil or alcohol dye doen't require wiping.

Spraying dye tends to be the best way to get an even color. It does take some practice.

Clear finishes should not look any different. When to project is finished no one should be able to tell if the finish was wiped-on, brushed-on or sprayed. Spraying is faster not better.

[Chris Fournier]

I think that Scott makes some valid points right up until the end of his post and then I have a different opinion from Scott.

"Clear finishes should not look any different. When to project is finished no one should be able to tell if the finish was wiped-on, brushed-on or sprayed. Spraying is faster not better."

Scott Holmes

To make this statement Scott is making the assumption that every clear finish is being meticulously rubbed out and this is not reality. Not every project budget has room for a properly rubbed out finish - nor should it.

If your brushed finish looks like a sprayed finish, then you are either the best "brusher" on Earth or you have figured out how to create orange peel with a brush or both.

Spraying is faster is for two reasons, one it is faster to apply as a finish transfer technique and two, if applied correctly and only a minimal film is required you can achieve a "finished" finish right off the gun lickety split.

Also many clear finishes are designed to be sprayed. With these finishes spraying is not only faster than other techniques, it is required.

Depending on the finish used it is possible to tell the difference between spray finishing using a convential gun setup (high pressure, low volume) and an HVLP setup (high volume low pressure), not just the differences between spraying, wiping and brushing.

The real trick with spray finishing is developing the ability to match finish viscosity with the proper needle/tip assembly and "propulsion" which is the air pressure/volume used to transfer the finish from the gun cup to the furniture surface. If you can do this you will have achieved proper atomization and wet film build. Once you can do this you can become an expert by tweaking the wet films ability to stay wet long enough to level almost perfectly and not run or sag.

To get proficient at spray finishing I would recommend that you do the following:


Develop good gun technique - the books you mention can really help you here. You can practice with water to a certain extent. This is cheap and saves the environment.
Research by all means possible and develop a close relationship with a local finish supplier that provides a broad range of finishes and good technical information.
Always test before committing to the project proper.
Take notes about how you thinned, retarded your finish and the ratio. Did you thin your spar varnish with mineral spirits or naptha? Did you add Japan dryer? Your recipe is very important if you want consistent results. USE SOME KIND OF VISCOSITY MEASURING SYSTEM like Zahn for instance. This will help you use the finish as the finish formulator/manufacturer intended.
Take notes about the tip/needle setup and pressure settings.
Work with one type of finish and become proficient with it before you try another type of finish. This will help you really learn the lessons that this finish has to teach you. Trying to get good at spray finishing while jumping between shellac, spar varnish and a "two pack catalyzed" finish will leave you scratching your head and wrecking a lot of work.
Try to develop your skill set and processes so that you can get the quality of finish that you require with the least amount of materials - this includes how you clean your equipment!
Try spraying clear finishes for a while and once you have achieved some success you can move into spraying with colour be it dye or paint.
I think that you'll enjoy spray finishing quite alot. In many cases it is the only way to apply the finish that you want to use or to get the effect that you're after. The fact that it is fast is a bonus, in many cases it is better than other methods of applying the finish of your choice.
All of this being said, don't force the technique on a process that begs to be brushed, wiped on or even dipped!

[Scott Holmes]

Chris,

Your points are valid. "out how to create orange peel with a brush" LOL

[Chris Fournier]

Like I said Scott, that would take one fine "brusher"! Faux orange peel - would there be a market for that?

[Trace Beard]

Scott and Chris, thanks for your help.

Trace

[Howard Acheson]

If you are new to spraying, spend a lot of time learning your equipment and learning how to spray. You don't just pick up a gun and magically get a good finish. Spraying has a learning curve. Start by spraying cardboard boxes--inside and out. Learn how to "read" the spray and the finish on the surface. Learn what the ajustments on your gun and air source work and what they do. Learn how different finishes handle. Lacquer is quite different from oil based finishes. Waterborne is different from other finishes also.

In our shop, an apprentice finisher would spend a week or two learning how to spray before he was allowed to work on a real job.

[John TenEyck]

Chris's comments are spot on, IMO. I would add that spraying is not that hard to learn well enough for you to do work far superior to what you can do with even the best brush technique. I only started spraying a year ago, and in only a few practice sessions I was putting down very nice coats of water based topcoat. The real proof to me came when I started spraying toner where you can really see if it's not uniform. It was like someone had opened up a new door for me. If you're an amateur like me, you don't need to spend a lot of money to get into spraying, and high quality results are within your grasp w/o a long learning curve. The only downside of spraying is material yield and the need to have a clean space to do it. Oh yeah, and wearing that d.... respirator !