hot spray booth

[ouchmyfinger]

In last weeks night class, myself and another bloke were about to set up for spraying a high build primer on our project (avenger wing) when teach came over and stopped us, saying the booth was too hot and he put the coolers on to lower the temp, i asked him why and he said spraying in a booth too hot can cause all sorts problems with all sorts of different paints , so guys tell me why and what would happen ! so i can impress him with new found knowledge on wednesday

 

[norsa]

Ideal spray temp is 20'. Above that, flash off is increased to the extent that the paint won't flow correctly and leave dry overspray and therefore inter coat adhesion issues. If he has other ideas it would be good of you to share.
Nick

 

[steveo3002]

really hot temps would cause the paint to dry almost instant and maybe leave dry streaks , patches etc

in practice it gets pretty hot in the summer in a oven, thats why theres slow thinners and hardeners etc

 

[ouchmyfinger]

Ideal spray temp is 20'. Above that, flash off is increased to the extent that the paint won't flow correctly and leave dry overspray and therefore inter coat adhesion issues. If he has other ideas it would be good of you to share.
Nick

nick yes the temp was way above that almost unbearable, the booth had been drying a load of panels earlier, i,l see if he can elaborate.
paul

 

[ouchmyfinger]

really hot temps would cause the paint to dry almost instant and maybe leave dry streaks , patches etc

in practice it gets pretty hot in the summer in a oven, thats why theres slow thinners and hardeners etc

steve, that makes a lot of sense also.
cheers both

 

[ouchmyfinger]

Nick, Steve, yea your both spot on , the primer starts to dry when it leaves the gun, congeals together and hits the car, it looks like someone has thrown a hanfull of sand on it. Also he said if the booth is too hot when baking off your gloss coats etc, you get what is called SOLVENT BLOB, this occurs because the outer surface is drying much too quickly making the solvent rise to the top looking like tiny globules, blobs.

 

[norsa]

There you go. Direct gloss and clears normally have 10% solvent content which has to flash off before baking but data sheets should give you this flash off time at a given temp.

 

[ouchmyfinger]

Nick, Steve, yea your both spot on , the primer starts to dry when it leaves the gun, congeals together and hits the car, it looks like someone has thrown a hanfull of sand on it. Also he said if the booth is too hot when baking off your gloss coats etc, you get what is called SOLVENT POP, this occurs because the outer surface is drying much too quickly making the solvent rise to the top looking like tiny globules,

solvent pop not blob, as i said....