star hvlp spray gun

[Bakes]

Guys,

I have a new star hvlp spray gun which is spraying only a small amount of paint. The pressure at the gun is all good and i have played with the liquid control control but it doesn't make any difference. when i clean the gun and spray water and turps the amount coming out is plenty. does this mean my paint needs to be thinned more, i have thinned to 80 odd % paint?

Cheers,

Bakes

[durwood]

What type of paint are you trying to spray?

[Bakes]

british paints acrylic

[durwood]

acrylic lacquer
acrylic enamel
acrylic urethane enamel
water thinned
solvent thinned

???

[martrix]

Im tipping it water based acrylic, thick as glue. Prolly tring to jam it through a 1.2mm nozzle.

[addo]

I'd assume water-based acrylic paint, too. It may well be a 1.4mm nozzle. Try adding up to the maximum amount of water as suggested per the can, then reduce with Floetrol as required.

After all that, a 2.0 nozzle would be better...

Regards, Adam.

[durwood]

I guessed it was water based household acrylic enamel also. but there was a possibility its not. The wife bought home a tin of enamel the other day, she thought it was turps based enamel it was waterbased. Only difference in the labels was the word acrylic before enamel . Exactly the same label both types next to each other on the shelf. The girl at Bunnings said to her when she took it back "that happens a lot people get them mixed up all the time"!!!!! I was making the point that if there is little information or misleading information its difficult to give proper advice.

Same goes with the gun as both Matrix and Adam have pointed out, what is the actual spray gun set up to spray? If the nozzle and air cap sizes are wrong (and they probably are as water based paint is not the norm to spray) any thinning or adjustment to the air pressure will be of no use, it will spray badly and you would be better off with a brush or roller.

If the paint is not thinned the right amount or the gun is the wrong size for such paint or both are wrong it will not be easy to get any sort of a good result.

The gun purchased should be one suitable for what you intend to use it for just not a spray gun at $xx.00. If it does a lousy job you will then have to rectify the mess (or find you are unable to spray) and then get the right equipment anyway.

Bakes, check the instruction with the gun, it should tell you what the numbers on the nozzle and air cap are suitable for if, it doesn't say for lacquer take it back and see if you can one for lacquer. This will have the large nozzle as pointed out by Adam.

[Termite]

I regularly spray Dulux Aquanamel with a gravity HVLP gun. The recommended thinning with water is max 5%.
The BIG secret is to use a 2mm needle/jet. The other secret is to take the paint strainer out of your gun, if your paint is suspect then strain it before you put it in your gun.

[Bakes]

Guys,

Yer it is waterbased, and bloody thick out of the can. Thanks for the advice. i will take the strainer out and see how that goes. Can i assume i am better off spraying oil based paints?

I will have to see if i can get the larger nozzle from trade tools, i think i have read on the forum that you can get these, or maybe i just switch to oil based. i am spraying plantation shutters and only went with water based due to easy cleanup and less fumes.

Bakes

[durwood]

There is no point in trying to get a different nozzle, if you manage to get one that is say 2.0mm the air cap hole will not be big enough to go over it and the size of the holes in the cap won't be balanced for the larger nozzle. Also the needle will not fit as the smaller needle will not block the larger hole off. You have to buy what is termed a "set up" this consists of air cap nozzle and needle. They will cost neally as much as the gun itself so as I suggested before see if you can exchange the gun for a gun with the correct "set up" in it.

To spray paint you have to reduce the viscosity to spraying consistancy. Depending on the brand of paint and the temperature will depend how much thinner is needed to reduce it to spraying properly. It could be anywhere between 5% and 50% to get it right. Depending on the gun it will then evaporate as it leaves the gun and travels to the job. Unless you have a viscosity cup to measure the viscosity you have to guess and experiment until you get a satisfactory result. As water based paints (those for house hold use not car paint) are normally brushed or rolled the spraying info on a tin is often not mentioned. You could contact the company but you still need the equipment to measure it so the best way is to experiment until you get it spraying OK. It has to be pretty runny or it won't give a good finish thin it right down till it appears to be like milk. You will also have to have the gun adjusted proplerly to get a good result

Different paints require different amounts of thinner. Warer based paints need to be done acurately or they run easily as the water takes a lot longer to evaporate on the panel than a solvent in lacquer or oil based enamel would.

If you are going to switch to oil based paint make sure you are somewhere where the overspray can't drift onto things around it or you will have overspray on ever thing withing 100 yards.

[Termite]

Regardless of the above advice I would check on the price of a 2mm setup. I use a quality gun and a change of size is only around $30.00.
With water based paints, check with the manufacturer regarding thinning. As I said earlier, Dulux Aquanamel has a MAXIMUM thinning of 5% water.

If going to anything other than waterbased then you should be aware that some of the paints do have a longer "wet" time than waterbased. Overspray can be a problem, but remember that there is considerably less overspray with a HVLP gun. With a good setup a HVLP gun will put 80-85% of the paint onto the job, compared to a conventional which usually puts only 35% onto the job, the rest goes as overspray.

[Pusser]

I thought that when you Star provides a kit not just the nozzle - you get a needle to change as well. The guns are designed for multiple nozzles. That is why the Nozzles are relatively expensive - it actually is part of a kit. No where near as expensive as a new gun though.

[addo]

Yes, by "nozzle" I inferentially meant the nozzle/needle kit - which may or may not include the air cap (seems to vary!).

Regards, Adam.