spray guns 101

[merrill77]

When he heard that I had acquired a high-cfm compressor, a friend offered up his spray gun. He said it is a "Sharpe Platinum HVLP" - of which I see there are various models - and it is unused. I've asked him for the model number.

I _do_ intend to try spraying some finish in the future, but I know _nothing_ about it. I expect I'd like to spray poly (oil and water-base), laquer and maybe shellac. Maybe even water- and oil-based paint (e.g. house-paint). Are there specific guns I would or would not want to use for these? Are guns specific to certain types of finish? Help!

TIA,
C

 

[ScottM]

Chris no input on the gun type. I do not spray myself, yet, but I understand if you use oil and solvent based finishes you have to spray outside due to the potential health and explosion risk. That is unless you have a spray booth. Good luck

 

[merrill77]

Chris no input on the gun type. I do not spray myself, yet, but I understand if you use oil and solvent based finishes you have to spray outside due to the potential health and explosion risk. That is unless you have a spray booth. Good luck

I plan to do all my spraying outside, regardless of the solvent. I don't have a booth and don't have room for one.

 

[Travis Porter]

I am not an expert, so whatever I say may be inaccurate or not work for you.

With the gun you have, you should be able to spray waterbased lacquers, polyurethanes, etc with no changes. You can spray oil based products, but will probably need to thin them some to get them to spray well. You will need to get I believe what is called a Ford cup to time how long it takes a cup of the stuff to drain to see if it needs to be thinned or not. Personally, I have not tried spraying oil based stuff yet, but I intend to very soon. I have a couple of lap board/desks I have been brushing with polyurethane, and after spraying WB lacquer with moderate success, I despise to brush.

Spraying latex paint is a different matter. I tried it once unthinned in an HVLP conversion gun, and I regretted it. Others have had success with thinning the paint with water and or Floetrol and using a larger needle/cap set, but I have yet to try it.

I have sprayed shellac, and that is about like spraying WB stuff to me since it is thin.

Make sure to use a strainer on every finish you run through the gun.

Hopefully, the gun you have has a regulator right at the handle so you can adjust the input pressure. I am not sure of the adjustment configurations of your gun, but pretty much all conversion guns should have a pressure regulator adjustment, an air adjustment, and a fluid adjustment.

The fluid adjustment is just how much the needle is allowed to move back. When getting going, set your air pressure at the air compressor regulator to say around 60 lbs, and use a fairly large inside diameter air hose to your gun as these things take large volumes of air. At the gun, start with your pressure around 25 lbs. Have the fluid needle closed. Set up to spray on scrap, squeeze the trigger, and start opening the fluid needle until you start to get a fairly even spray coat. Play back and forth with the fluid and air controls to have the maximum amount of fluid with the least amount of air. The reason for this is the less air pressure you use the less "bouncing" of the stuff you are spraying so the less mess and less over spray.

If you do the above, you can spray inside as I do. I just open a window, stick a box fan in it, and go to it. I would NOT do this with a standard gun as the overspray gets everywhere.

Really, spraying isn't too hard with the WB products. Consistent and timed motions and steady hands once you have the flow laid out correctly, it can be quite pleasing.

Prep work and making sure your project is properly sanded is more important than ever because everything shows when you spray. They say spray finishing is an art, and I can see it. Fortunately, it is fairly forgiving, and once you get the hang of it, kind of fun.

PS - I stay away from the oil based stuff as well to keep gun cleaning easier.

 

[Ozzie-x]

I have not used a Sharpe HVLP gun, but I'm sure it will be nice. When I used to spray cars, Sharpe or Binks were considered the best standard pressure guns, HVLP wasn't around then. After you get the Sharpe HVLP gun, since it's new, it may still have the manual with it. The manual should explain the adjustments. If the manual is not with it, get the model number and look it up on-line at the Sharpe website and probably download a manual or contact them and get them to send you one. Most mfgrs are pretty good about making the owners manual available for free.

Update: here's a shortcut to the Sharpe site for downloadable manuals: http://www.sharpe1.com/sharpe/sharpe.nsf/Page/Spray+Gun+Manuals

 

[Ozzie-x]

I am not an expert, so whatever I say may be inaccurate or not work for you. With the gun you have, you should be able to spray waterbased lacquers, polyurethanes, etc with no changes. snip, snip, snip.

Good advice from Travis. I'll add a couple of things. Most spray gun mfgrs make different size needles, and you may have to get a different needle(s) (smaller or larger) other than the standard needle to successfully spray some materials. Particularly some types of paint can be problematic. If you are going to spray a number of materials, you will want to get a viscosity cup as Travis mentioned. The manufacturer's needle size recommendations are usually keyed to the viscosity of the intended spray material. As to spraying inside versus outside, I do most of my spraying outside since I mostly spray lacquer or solvent base materials. Especially with lacquer, if you don't have good ventilation, you will take a trip and never leave the farm, followed by a head splitting headache, DAMHIKT. Another note of caution, a friend sprayed water base poly on a set of kitchen cabinets in his shop and the waterbase overspray rusted all of the bare steel/iron in his shop such as the tablesaw and jointer tops.

 

[merrill77]

Another note of caution, a friend sprayed water base poly on a set of kitchen cabinets in his shop and the waterbase overspray rusted all of the bare steel/iron in his shop such as the tablesaw and jointer tops.

So I guess that ends my deliberation - I won't even be spraying water-based in the shop. Fortunately, I have a garage with doors on both ends that gets pretty good ventilation with even the slightest breeze (as well as areas on either side that are suitable for spraying in a pinch).

 

[pirate71]

I have a Fuji and just finished spraying cabinets and doors in both my garage and kitchen.

I used Benjamin Moore's water based primer and Impervo oil based finish coat. Both worked extremely well with the Fuji. The primer needed to be thinned with water about 25% and the oil needed to be thinned with paint thinner about 35% to get the right viscosity.

I setup a spray station in my garage. I put plasctic on long 2x2 lumber and set it on top of the garage door rails and wrapped the plastic around the side walls. Also, I put a fan with a filter in a window on the side of the garage. That setup took care of most of the fumes and took out enough of the overspray so that I had just a little dust in the other half of the garage where my tools were stored. I did not notice any problem with the water based primer rusting tools. I did not cover the garage doors and actually they did not get paint on them EXCEPT one small area where I had the gun directed toward the doors when I was first experimenting.

I might note that this is the first time I've ever used a spray gun and I found it pretty easy. It just takes some experience to get the feel for how things should go......how to get the gun setup right and how the material should be thinned(if needed).

Evans

 

[DavidF]

Some great comments above and I would like to add:
Just for info, I spray Target WB products with a cheap (ish) titan gun from Amazon. It has a 1.4mm needle set in and this seems to work fine.
30 psi at the input gauge.
If you do have a gauge at the handle it is important to keep the cheater valve wide open.
This valve is usually near the input of the gun and is only used if you don't have a regulator at the gun. You are looking for maximum fluid with good atomization - no blobs!
if you can leave the input preassure at 30psi and the bleeder open and the fan size on full, that only leaves one adjustment - the fluid control, and that makes the gun much less daunting!
I spray in side the shop with no special precautions other than covering up the machinery in the immediate vicinity with a plastic drop cloth. With WB stuff the over spray is dry before it has gone more than about 3' with HVLP.
Biggest thing I make every effort to control is the temperature. 40 - 80 deg are the extremes for WB, and I find 65 - 70 perfect. Keep the wood and the finish in this steady temp so that everything is nicely settled.
Don't use a fan type heater to avoid chucking up dust. Don't run an extractor fan that pulls air over the piece being sprayed, WB has to have time to flow out before it dries and the air flow will cause it to dry before it has a chance.
Don't hold the gun too far from the surface 6"-8" works for me, may be 10" max, again, WB dries quickly and any further than this and some of the droplets will be dry as they hit the wood and give a rough finish.

BTW - All this has been learnt the hard way, even reading books has not taken away from the fact that you need to do stuff and see the results, good or bad!

Brushing is a thing of the past for me because when you get it right there is no surface like it without a mass of "post processing"

Have fun!

 

[DaveD]

Haven't sprayed in years but here are some cautions I have learned from experience.

If you spray in the garage and the door is up you will get over spray up over the door and won't notice it till you close the door (and then it is too late). Throw a tarp over the door if its in the up position.

The thickness you are spraying on is very deceiving. One minute the vertical surface looks beautiful and the next minute you notice it is all running down hill. Did this with a 16' garage door years ago.

Get a smooth sheet of masonite and practice on it before trying something you care about.

If you spray inside you want to tape over any house heating registers you have in the shop. The heat/ac will come on when you least expect it and cause all kinds of problems. Its even more important to not have a cold air return in the spraying area.

If you set up some kind of exhaust fan and plan to EVER spray anything other than water based you need an explosion proof fan. BTW an explosion proof fan only confines the explosion (if it occurs) within the fan itself so the room doesn't go boom. That assumes you 'pot' the wires to the fan correctly.

Bases on the size fan you use (and how long it runs, might take hours) it may suck heat out of the house on a cold day and the temperature in the house will start to go down. It will do the same in the summer and you will lose the cold air. I used to run mine for hours to help exhaust dust.

Put filters on either the inbound or outbound side of the fan or you will find that it puts a nice coating all over everything on the outbound side of the fan. Luck for me it was dust rather than paint on the outside of the house.

Painting needs a good filter on the line and DRY air. Did I mention it needs DRY air?
You need the right respirator/mask based on the kind of material you are spraying. Now is not the time to buy it from Harbor Freight to save a buck or two.

Having seen your house I'd think about taking a garage bay and setting it up so you can hang cheap tarps or plastic and make a poor mans spray booth that can be easily put up and taken down. If you do spray outside and spray color be VERY AWARE of over spray you may not see. You don't want to hear 'Dear, what is this rough dust that is all ver the outside of this window?' and then you notice it is also on the outside of the house.

Personally I think it is a hassle and waste of time to spray if you don't have a dedicated area always set up to spray or it is a very large project.

You are on another tool slippery slope now that you have the air compressor. Enjoy.:eusa_danc