problem with spray gun finish

[garfield]

Hi All,

I'm spraying enamel paint through a gravity feed spray gun which I have thinned using enamel thinners, I have thinned the paint 15%.

I notice when I spray the finish looks as though It's wet in some spots and some spots look as though they are dry... It's not a good look and I'm wondering what it is I'm doing wrong..??

Can someone please tell me if it's maybe not thinned enough - or it is thinned too much, or maybe if I need to fiddle with one of the adjustment knobs on the gun?

Really appreciate anyone with some advice

Thanks
Geoff

[wheelinround]

weather can cause this, humidity and it drying it out to fast.

How are you spraying it as in the application movement side to side with overlapping happening??

whats the spray pattern like??

Are you keeping the same distance from the work not an arc motion??

[garfield]

Hey Wheelin,

Yeah I did keep the same distance for each wave and I'm pretty sure I've kept the spray close together too.

As I said I thinned it about 15% but I almost get the feeling when I spray that it just feels thick and needs even more thinning.

The paint is about 2 years old and has been closed for a while and there's some thick blobby parts in the tin do you think its OK to thin it more to get a consistent amount coming through the nozzle..?

Thanks
Geoff

[wheelinround]

Geoff sounds like a clogged jet or air or even build up on the tip. without being there its hard to tell for sure. what pressure ?

For old paint I used to thin 1/3rd up to 25% stir till I couldn't stir no more strain through old pantyhose x 2 one on the tin one on the pot. One on the pot push centre down otherwise it will flood over, remove when you have what you need and a squeeze from tip to toe this gets the pigment through don't bust them or you have to start again.

[Harry72]

Sounds like the gun isn't atomising properly, put some turps in the gun and spray a constant stream listen for "whisping" sounds if it is you have an air leak inside the gun, strip it down and fully clean it out then pay attention to all threads and mating surfaces, some thread tape can work wonders.
Cheap guns are poorly machined so mating surfaces can be leaky, corrosion can cause probs too, I have before spun up nozzles in a lathe and cleaned them up with some W&D paper enough to seat better.

Enamel is about the hardest paint to spray other than candy apple paint, many people spray it with to much pressure(air pushes the paint around on the surface, causing thin and thick parts that run...) and thinned out to much, enamel likes on top coats to be put on thick at the point just before running it needs this to flatten out too a nice shine(much like full gloss polyU)and never ever respray over it anymore than 1~2 minutes it causes surface tension problems and you get massive orange peel IMHO. Also over spray will kill the finish if its a big project like a car, draughting is needed.

[garfield]

Thanks for the replies guys.

i pulled my gun apart this morning and around the pin it was disgusting! it was like a build up of thinners and Metho and paint.

Is it common practice to pull the gun apart every so often and give it a proper clean? ever since I've had the gun the only way I've cleaned it is either with thinners or metho by spraying it through the gun.

Is there a good website on maintenance and cleaning tips for spray guns?

Thanks
Geoff.

[wheelinround]

Here's one on airbrushing Tips and Tricks - Airbrush.com (http://www.airbrush.com/tips-and-tricks.aspx) many good tips do a google on how to spray paint and you'll find many more.:2tsup:

[garfield]

Cheers Wheelin.

May I ask how you clean your spray gun please?

[wheelinround]

Haven't for a long time but when I use it if its air operated I empty everything out pour in some thinners swill the pot round after giving a quick spray into a rag or at something wasteful. Then put my finger or thumb over the tip and push and spray this back pressures into the pot mind your eyes as spray can escape through the breather hole.

I pour that out wipe and put it away I have only ever pulled it apart a couple of times once when a seal went and another time boss left paint in it :((.

If its been used day in day out maybe left to soak overnight in thinners. It now almost 30 years old.

Oh that breather hole if it gets clogged or blocked during spraying (ie paint around it) causes problems also.

[Harry72]

The gun should be stripped down after every time its used, some finishes like shellac and lacquer which readily dissolve in their appropriate thinner can be left without to much trouble if using over a few days.

[garfield]

Thanks to both of you Wheelin and Harry for your adive.

I've decided from now on I'll just do a complete clean after every use so that I know it will good for every use after.

Thanks
Geoff

[Dengue]

thanks to wheelin and harry for this valuable advice. I am a spraying newbie too, and found it very relevant. If spraying water based primer, and it takes 3 hours to dry, do you empty the pot between 3 hourly coats? What about thinned enamel paint being sprayed?

[WillyInBris]

Jill do you have a spare pot? if so fill it with water and run it through as for the pot with paint in it I just put some glad wrap over it and put it in a cool cupboard it works fine and at the end then I do a full clean like the others.

I normally paint over two days just give the pot a stir before I use it.

Willy

[Dengue]

thanks willy, that sounds good. How do you manage this with thinned enamel paints?

[wheelinround]

thanks willy, that sounds good. How do you manage this with thinned enamel paints?


If your talking about leaving it in the pot between coats thats ok just if air operated back pressure a little as above and store in the coolest place (we used to have a fridge at work). Before using do a stir.

[Harry72]

You can leave the enamel in the pot Jill like wheelin said but you must still clean the gun out fully if leaving it for more than 20 minutes or so.

[Dengue]

thanks Harry, do you mean strip the gun down between coats, or just use another pot with thinners and squirt that through?

[Harry72]

Between coats on enamel(not that quick dry crap)should be a minimum of 12hrs so yes the gun will need cleaning, personaly I would clean the pot too because the paint on the side walls above the paint level will cure and will need stripper to remove it.

[wheelinround]

:whs:

[wheelinround]

I sort of recall going over this 12 months ago with Garfield often good to do somethings again.:rolleyes: