Spraying water based finishes

[Pete F]

I have reasonable experience spraying auto and to a lesser extent oil based house paints, now using a HVLP gun which I've previously had good results with.

In the past week I've tried spraying some water based poly (Cabothane) and now some water based acrylic (Dulux Weathershield). Both finishes should have been high gloss.

While I appreciate the level of gloss won't match a good oil based finish, I'm a bit disappointed in the level of gloss I've achieved in both these situations. I was using a 1.4 mm needle/cap, spraying at 40 psi and thinned to get good atomisation. I'm going to try one last coat (3rd) of the acrylic and this time and think I'll change to a 1.8 mm needle/cap and possibly not thin as much. From the can the acrylic requires quite a bit of thinning and I wonder if that's affecting the curing. Otherwise the flowout seems ok and I'm getting quite a good surface, but more like what I'd describe as "semi-gloss".

How are others going with similar setups? Any suggestions to improve the situation? Being used to stinking solvents, iso-cyonates, and other miscellaneous crap they put in the paints I'm used to, water based sure would be good .... if I could get good results!

Pete

[Bob38S]

G'day Pete,

Not sure if this is what you are after but - instead of thinning with water, try "Flotrol" - from the Flood company - available at all of the usual suspects. I've used this successfully to thin paint sufficiently for spraying. In the past, thinning with water has "knocked off" the gloss and made for poor coverage when dry.

Just my very limited experience, regards,
Bob

[munruben]

HI pete, Airless spray equipment is the only way to apply acrylics and water based paints satisfactorily. You have to dilute the material so much with air spray method for it to atomize that the paint has lost its lustre.
Go airless and you will see the difference.

[munruben]

BTW, I assume you were talking household acrylics and plastics and not automotive paints.

[Pete F]

G'day Bob, I was about to try Floetrol when I read that it somewhat reduces the gloss level, precisely what I was trying to avoid. I contacted Dulux and they said max 15% reduction. The larger needle didn't help, and it needed 25% or so to atomise! I agree, an airless would be able to pump it easier, but I'm not about to go out and buy a setup just for this type of work.

I've finished this job now, did a final pass and it looked ok when I left it last night. Goodness knows what it will look like this morning

[Strom]

Hi Pete..
You deffinatly wont get the same sheen level out of the domestic acrylics as you do with the Enamels..
If your getting good results with your current spray set up just not happy with the gloss level, The aqua enamel will be your best option in the domestic acrylic range..

And Correct I wouldn't add no more than 15% Flotrol..
(Obviously this does impact negatively on the gloss level)
Goodluck..

[Pete F]

Cheers guys. I haven't used Floetrol before, so did some research before i was going to use it and 90% of it was positive. However a few pro painters seem to think it was completely unnecessary if using good quality paint, and more something to help out cheaper paints. One thing about this Weathershield is it's VERY thick in the can, too thick in my opinion even for brushing/roller. Maybe it's to help punters avoid runs, I don't know, but it was definitely inhibiting its flow out when brushing, and I use very good brushes (and care for them like they're my kids )

The end result is that the job is pretty much done. The final effect was "ok", a bit screwed up where I just blew a coat over some dodgy areas, but hey, this isn't a Rolls Royce I'm painting. However one thing was a "film" on the surface looking much like flat sawn ply or damascus steel. As it turned out it simply wiped off with a bit of water and a micro-fibre cloth.

I have a garage door I need to paint and will try to spray again. I have a still larger needle and cap, 2.4 mm IIRC I normally use for spray putty. I'll give that a go and see what happens.

Pete