bubbles in cup

[ian groves]

well today I was painting along and I noticed I was getting a touch of paint coming out when I just pressed the the air and then after another 5min or so I started getting bubbles in my HP-CS so I stripped the ab down full and give it a really good clean ,put it together and still same,i have had this ab apart and together about 10 times and I have tried using a fine paint brush dowt the fluid nozzle to see if anything in it and I really think its nice and clean now ,its been in the ultrasonic for about 10mins in total and still same ,
at one point I tried just putting the cap on and no fluid nozzle trying to illuminate the what was wrong and even with the fluid nozzle off it is still bubbling ,please someone help me as im going nuts with it here .

 

[jagardn]

Bubbles in the paint cup is a bad seal between the airbrush body and the nozzle.

 

[Madbrush]

Bubbles in the paint cup is a bad seal between the airbrush body and the nozzle.

I'm inclined to agree with this since "ultrasonic cleaner" was mentioned, if you are using one these regularly and your nozzle has a rubber seal, good chance that seal has shrunk a little and your nozzle is sitting too far back now allowing air to enter back into the nozzle aperture, (I spelled that without spell check,).

Solution? easy, if you don't to buy a new nozzle, get a new nozzle seal ring or apply the tiniest amount of plumbers (PTFE) tape, could also try bees wax, just make sure the bees are asleep when you take it, they can be temperamental little buggers.

 

[matty171]

well today I was painting along and I noticed I was getting a touch of paint coming out when I just pressed the the air and then after another 5min or so I started getting bubbles in my HP-CS so I stripped the ab down full and give it a really good clean ,put it together and still same,i have had this ab apart and together about 10 times and I have tried using a fine paint brush dowt the fluid nozzle to see if anything in it and I really think its nice and clean now ,its been in the ultrasonic for about 10mins in total and still same ,
at one point I tried just putting the cap on and no fluid nozzle trying to illuminate the what was wrong and even with the fluid nozzle off it is still bubbling ,please someone help me as im going nuts with it here .

Hi ian, there could be a couple o things wrong but anytime ive had bubbles in my cup its been due to a damaged nozzle, cracked or split, as already stated its due to a bad seal somewhere. As for pushing down for air and paint coming out that tells you that the needle wasnt properly seated, it its not fully pushed forward or there could be the tiniest speck of paint, if you have a magnifying glass look at the tip of your nozzle see if you can see any damage, even the smallest crack can cause problems

 

[Madbrush]

Hi ian, there could be a couple o things wrong but anytime ive had bubbles in my cup its been due to a damaged nozzle, cracked or split, as already stated its due to a bad seal somewhere. As for pushing down for air and paint coming out that tells you that the needle wasnt properly seated, it its not fully pushed forward or there could be the tiniest speck of paint, if you have a magnifying glass look at the tip of your nozzle see if you can see any damage, even the smallest crack can cause problems

I concur

 

[Squishy]

I'm with matty too. There is also the possibility that you have slightly flared out the end of the nozzle, which is why the needle isn't sitting correctly, and something that is hard to tell with the naked eye.

 

[MeeshellMP]

See that, the answer BAMB!! just Like that ol I agree with all of the above

 

[ian groves]

panic of and sods law I spend an hour stripping and cleaning over and over and then though ill put some

Hi ian, there could be a couple o things wrong but anytime ive had bubbles in my cup its been due to a damaged nozzle, cracked or split, as already stated its due to a bad seal somewhere. As for pushing down for air and paint coming out that tells you that the needle wasnt properly seated, it its not fully pushed forward or there could be the tiniest speck of paint, if you have a magnifying glass look at the tip of your nozzle see if you can see any damage, even the smallest crack can cause problems

Cheers Marty
There a very sensitive tool for sure never had this with a pencil haha.daft question is why does it bubble back when the seal around a threat is not sealed proper for what ever reason. Hopefully it's ok now as only sprayed water out before as was losing the will to live.
Fingers crossed as see how it goes tomorrow
Thanks all for the reply

 

[matty171]

panic of and sods law I spend an hour stripping and cleaning over and over and then though ill put some

Cheers Marty
There a very sensitive tool for sure never had this with a pencil haha.daft question is why does it bubble back when the seal around a threat is not sealed proper for what ever reason. Hopefully it's ok now as only sprayed water out before as was losing the will to live.
Fingers crossed as see how it goes tomorrow
Thanks all for the reply

I have wondered this myself as to why a cracked nozzle send the air back down into the cup, and im willing to bet a more educated AB'er will be along to explain the science behind it.

 

[basepaint]

The science behind it is easy your trying to force paint and air out a smaller hole in the front of the airbrush then the larger hole going back in the cup and air will go to the path of least resistance! hence back into the cup!

 

[matty171]

The science behind it is easy your trying to force paint and air out a smaller hole in the front of the airbrush then the larger hole going back in the cup and air will go to the path of least resistance! hence back into the cup!

Ok going by what you have said if you damage the front of the nozzle say a crack or split, then there would be a larger hole at the front end so why does it push it back. Im not doubting you mate im just curious

 

[basepaint]

Becouse your still trying to push Both air and paint(where air will go back in the cup without trying to push paint with it)Kind of like a leak in a fuel line before the pump will suck air and not fuel becouse the fuel is heavery/thicker then the air)and if the leak is after the pump it will spray the fuel out the hole due to the hole going out to the lower pressure outside the line

 

[Immortal Concepts]

Paint flows inside the nozzle and air flows on the outside. The only thing keeping them apart is the metal to metal seal. It's because of the venturi effect. Atmospheric pressure is why it flows into the cup because paint is below atmospheric pressure and air is above.
If it's cracked it messes up the venturi effect (how an airbrush works) and science takes over basically. Think if it as reversing the flow. This is why you can spray air and not have paint come out until you pull the needle back opening up the seal between the needle and nozzle, mess that up with a crack and the seal is messed up and to repeat myself, atmospheric pressure takes over. Basically same thing base said, just a bit more technical i guess . I'm sure I could explain better if I wasn't so tired right now. Just research venturi effect and it should make more sense matty.

 

[basepaint]

Thank I.C Sometimes I get to High tect

 

[splasha]

Any tips on cleaning the little buggers properly, then?

 

[matty171]

Thanks basepaint and Justin, sort of understand it now, will be googling venturi effect over the weekend

 

[ian groves]

Thanks basepaint and Justin, sort of understand it now, will be googling venturi effect over the weekend

Think there Was a film falled the venturi effect hA

 

[Madbrush]

Think there Was a film falled the venturi effect hA

That was Ace Ventura who was also full of air, ha ha ha

 

[Immortal Concepts]

Any tips on cleaning the little buggers properly, then?

Flush out your airbrush the second you are done. Maybe it's just me but I have never had issues trying to clean my airbrush as its always clean. Of course using uro helps tons cause of solvents but even with waterbased if you don't let it sit, and repeatedly flush it out (i unchuck my needle and push and pull it while pressing down for air and it cleans the nozzle right out, just be gentle so you don't deform the nozzle. I will do this about 3 times of filling the cup and using this method. Has worked for the past 10 years without fail for me.

 

[Squishy]

I very rarely get problems with my nozzle now. I used to reduce my paint less, and it flowed well enough, but found it hard to get the nozzle squeaky clean. Since reducing more, have had way less issues, and just make a couple more passes to get the colour density I want, and also make sure paints with larger pigment such as white etc, get a little bit extra reduction. Also I always filter the paint, and I flush through quickly with water at each colour change. I make sure I keep the paint well mixed, I have noticed a couple of times depending on colour that some mix with the reducer better than others, and the thinner paint comes out first, leaving a thicker paint behind which can cause a blockage. Give it a shake now and then to keep it mixed, and add a drop or two more reducer as the level gets lower if you think it needs it. And as mentioned above don't let it sit for too long.

All I do to clean is take the needle out, and wipe it. Wipe out the inside of the cup, then back flush it with water, and dump it out and do a couple of times if needed. then fill cup with water spray half through. Then replace the needle, spray the rest of the water and like Immortal move it back and forth carefully as I spray. usually that's enough, but I always refill the cup do it again just to be double sure. Check the spray pattern as you spray to make sure it looks the right shape, and isn't coming out less on one side etc. Then you're good to go.