My experience spraying finishes.

[yuri]

After long, I mean LOOOOOOOONG, period of fear of spraying finishes, I finally started to do it. I am glad that I did it and wanted to share my experience on that journey.

I was doing partial kitchen remodeling for my house and I needed to make additional cabinets matching existing ones. When it was time to finish the doors for them (the cabinet itself I finished with brush as I always did) I decided to spray. I have two compressor and larger one, 15 gallon Dewalt, looked like good entry candidate. I read a lot about HF purple spray HVLP gun. I went ahead and bought one. I started spraying, thanks god the weather was cooperating with me, because I sprayed at entrance to my garage based shop. After some playing I finally did the doors. WOW! I was impressed how good it came out, how approachable whole process is and how quickly everything is done. Now I am thinking why I waited so long!

Well, now I am on another project which requires even more finishing. I decided to use Hydrocote Polyurethane (water based). I'd prefer to make minimal thinning with water, but HF do not offer wide variety of needle/nozzles for the gun. I decided to buy nice gun and ordered QualSpray AM-5008 gun from Jeff Jewitt (homestead finishing products) with a set of right needles/nozzles. When I spayed red oak panels I found that finish is not that uniform compare to one I got brushing it. Red oak, being open grain wood, has smooth areas and rough ones. When I brushed the finish, after three layers the difference between rough and smooth areas become less noticeable, though still noticeable. But it was not a problem because I did not pursue to get piano smooth surface. When I sprayed, however, I did not that effect, it looked like finish little bit beaded on smooth surface and little bit emphasized rough area. Why it could be so?

[jteneyck]

......   When I spayed red oak panels I found that finish is not that uniform compare to one I got brushing it. Red oak, being open grain wood, has smooth areas and rough ones. When I brushed the finish, after three layers the difference between rough and smooth areas become less noticeable, though still noticeable. But it was not a problem because I did not pursue to get piano smooth surface. When I sprayed, however, I did not that effect, it looked like finish little bit beaded on smooth surface and little bit emphasized rough area. Why it could be so?

Congratulations on moving up to spraying.

Have you sprayed with your new gun and that finish on something other than red oak?  If so, does it produce a nice smooth finish?  In other words, are you sure the problem is with the red oak and not with your gun?  I have no problem spraying WB finishes on red oak.  I use a Qualspray AM-6008, BTW. 

Three brushed coats of finish is a lot thicker than 3 sprayed coats.  My guess is you aren't putting on wet enough coats when you are spraying.  Get yourself a wet mil gage and learn to apply the recommended thickness for the finish you are using.  Three coats, scuff sanding between each coat with 400 grit, should give you a smooth finish.  The pores will not be filled, of course.  You would need to use a paste wood filler to fill the pores if you want a completely flat and smooth finish.  

John

[Snipe Hunter]

jteneyck is probably on the right track here.

You might be describing a "Dry Finish" which is caused by either moving your gun too fast, holding your gun too far away from your work, spraying inside corners and getting blow-back, not not getting enough air through your gun to properly atomize your finish, or not getting enough finish through your gun, too wide a spray pattern or spraying in too hot an environment or spraying in direct sunlight. Lots to consider but all can be cured.

What you'll find about finishes is that they are all different. They all react differently to many things: Heat, humidity, the size of air-cap, spray nozzle etc. You can't possibly know what and why things are happening all the time. So what you learn to do is to adjust the way your spray.

You'll learn to speed up your passes with the gun, or slow it down. You'll learn to see your "wet edge" better by tilting your head and using reflected light to see the edge better etc. You'll learn to pull the gun back or get it closer to your work. You'll learn to visually identify what you need to do in order to lay down a nice finish. And that takes experience.

Top coats require a wet finish. Wet enough to get a smooth finish and dry enough to prevent sags and runs. I've been spraying a long time and I still get sags and runs on occasion.

I've also learned to buy products that spray well. And that comes from trial and error. Every gun is different and every finish sprays differently so find what works best for you and your gun. I also try not to adjust my guns. About the only time I do adjust them is if I'm doing a very small job or repair and need to dial everything down to control over-spray or when I clean a gun and put it all back together. But, I usually just remember how many turns of each knob it took to disassemble it and put it back together the same way.

Generally speaking, most issues while spraying can be overcome by adjusting your pass speed and the gun's distance from the work. We call this "Speed and Distance". Speed and Distance is pounded into your head when you are learning to spray in a body shop or training environment. It's "almost" always the problem.

A couple tips:
Establish a baseline adjustment on your gun and work from there.
*Open up your spray pattern (fan height) all the way and then back it down to about 3/4. You'll get more concentrated finish and the edge of the spray pattern (fan) won't be as dry.
*Overlap each pass about about 50%.
*Close your fluid knob all the way and back it out about 1/4 open or till your see a nice amount of spray coming from your gun.
*Hold your gun about 10" from your work.
*Move your gun about 1ft per second.
*don't stop, keep the gun moving all the time.
*don't let go of the trigger at the end of each pass or you'll get "spit" when you pull the trigger again.

You probably will never have to adjust the spray pattern (fan). Unless you are doing something small or doing inside corners.
*If you get runs, either speed up your pass or turn your fluid knob clockwise to cut back on the fluid but remember your baseline.
*If you still get runs or orange peel, back off your distance.
*If the finish is rough (dry or poorly atomized) , slow down your pass or open the fluid nob (counter clockwise) remembering your baseline.

Orange peel and runs are usually caused by the gun too close the work, moving the gun too slow or too much finish through the gun.
Rough/dry finish is usually cause by holding the gun too far from the work, not enough fluid passing through the gun or moving the gun too fast.

IMHO, find a product that sprays well for you and stick with it.

I pay about $460 for a gallon of clear-coat and it's hardener and reducer. People think I'm crazy but the time it saves me because I don't have to wet-sand and buff to get a nice finish more than makes up for the cost of the product. My work looks better and I don't have to work harder to make it look that way.

Some finishes just don't spray well imho. They are sticky and cling to the spray nozzle and make life difficult.

Get a can of Deft Brushing Lacquer from Home Depot and thin it 10% with lacquer thinner and practice with it. It's cheap and looks good. Get your gun dialed in with something cheap like that. Then get spendy and buy higher end finishes.

There's more dust indoors than outdoors except during the pollen frenzy in the spring and always wear a mask.

[Bill Wilson]

Neil,

Thanks for the spraying tutorial.  This is definitely C&P and save worthy.  I spray shellac and have done it enough that I can do a passable job, but haven't ventured on to lacquer or waterborne finishes yet.  I have several books on finishing, which all cover spraying to some degree, but your explanation is about the clearest one I've read on how to get a good finish.

[yuri]

Guys,
I started not in the vacuum and read a lot on spraying, so theoretically I am prepared but all that way far from practical experience. Thank you for wealth of information, definitely will follow all useful tips and advises as I progress, though I am just hobby woodworker, not that much things I can build for quick progress :-)
For now I use spray gun just for WB finishes, mostly urethane. On my last project I used Hydrocote polyurethane from Hood Finishing Products. It's not that known or popular among hobby woodworkers, but some professionals woodworkers and musical instrument makers uses it. I bought it out of curiosity, some folks said it is very good product and not expensive. I can not comment yet how good it is for spraying, in comparison to other, but I like the finish itself, looks durable, levels well and i like the look with the hint of amber to it and dries not longer then most similar finishes. Most such finishes feel delicate after initial drying and get more durable with time as they completely cure. Hydrocote feels more substantial right away.

[Rob Young]

Just so you can be consistent if you start comparing how various finishes spray, pick up a $10 Ford #4 cup.  This way you can say (more or less accurately since there is a strong dependence on temperature) that you have thinned different finishes consistently.  Amazon has them.  

I don't spray frequently enough to feel comfortable just using the Mark I eyeball so as I experiment with a new finish, I keep a few notes and the cup time is one of them.

[Snipe Hunter]

Neil,

Thanks for the spraying tutorial.  This is definitely C&P and save worthy.  I spray shellac and have done it enough that I can do a passable job, but haven't ventured on to lacquer or waterborne finishes yet.  I have several books on finishing, which all cover spraying to some degree, but your explanation is about the clearest one I've read on how to get a good finish.

I wrote a book once about spraying called Spray Finishing for Dummies. It was one page long. Never found a publisher.

[Rob Young]

I wrote a book once about spraying called Spray Finishing for Dummies. It was one page long. Never found a publisher.

Item 1: Do not look directly into spritzy end.

[Snipe Hunter]

Item 1: Do not look directly into spritzy end.

Lol, It was in the book. Right by the warning label "WARNING This book may cause paper cuts. Don't look into the spritzy end of the spray gun"

[yuri]

I got ford #4 cup. Any resources I cold read through how to use it? Well, how to measure is pretty straightforward, but understanding what needle/nozzle combination to use depending on measured viscosity to use is not obvious.