the runs

[Petefeet]

morning all - i wonder if you could help a newbie to spraying?

last weekend i had a go at topcoating my camper - using lechler macrofan at 2:1 + a splash of fast thinners. apart from the gun stopping and starting a bit (solved by adding a bit more thinners in the second lot) i did seem to get a lot of runs which now need sanding out and another top coat applied.

so i was wondering - should i have applied the first coat quite loosely and let it tack first? (ie not gone for the 50% overspray), used more or less thinners?, given up as it was only just 15 degrees in shade?

are runs less likely/less impact as it gets warmer?

thanks for any advice - this is the hardest bit of the resto so far!
pete

 

[richie00boy]

How long did you leave between coats?

Sounds like you have a problem with your gun which adding the extra thinners helped to mask. But with the extra thinners you made the mix too thin. What size tip was the gun?

 

[Petefeet]

well - its a devilbiss gravity flg with 1.4 tip. it did seem to stutter a bit then pick up, so i then fitted a guage at the gun which showed that i had to up the pressure at the tank a bit to get 2 bar with the trigger pressed. its also going through one of the filters in the base which might impede the flow.

Now that i run over things in my head, I recall i left the paint about 45mins to an hour before i sprayed (as my mum and sister came round for tea darn it) so maybe the fast solvent evaporated and made the first mix too thick? and then as you say i over compensated and made the next too thin?

hmmm - a couple of things to think about there! how about the temperature and the first spray? Watching that restolad on utube (linked from another post here) he goes for a tack coat first which he says helps the next to grab on to? any merit in that ?
thanks
pete

 

[Daz1968]

I would think its down to gun set up and technique as I am also a beginner and have had some issues with runs but it was always an application error including putting a second coat before the first has properly flashed

 

[Petefeet]

hmmm - and i'm thinking that perhaps i had too much volume for base and not enough of a fan either. I guess you have to know your gun!
pete

 

[the snooper]

if the gun is stuttering you need to check the gland nut near the trigger that the needle passes through to make sure its tight enough not to allow air in but not too tight so it grips the needle, i doubt the thinner would have evaporated but leaving 2k in a gun for an hour and then using it is asking for trouble as it will start to go off, also if you wasnt in a heated booth did you use standard or fast activator, not heated you should have used fast

 

[pedrobedro]

On a gravity gun make sure the cup is vented as well or the paint can get airlocked and come out hit and miss. Runs are usually too much paint due to adjustment, gun too close to the surface you are painting or travel too slow or a combination of all the afore.

 

[Petefeet]

All very helpful lads; I suspect a bit more time setting up may be in order!

 

[chunkolini]

Looking at the title I thought you had been drinking perry.

 

[mr paint]

Runs are caused by many factors .

Gun set up

air pressure to low

fluid to far open

not holding gun at 90 deg to object

air temp to low

2:1 mix should not req any more than 5% thinners through a 1.4 tip


hope this helps

T

 

[PSweeney]

also watch your spray pattern. You maybe inadvertently converging on one point at the end of a pass

 

[Petefeet]

Thanks again - it's a perfect weekend to get this job done in the spring sun!
Pete

 

[Petefeet]

Tried again and still getting a few - but I spose I just need to sand them away and polish up to remedy?
P