Thinning enamel paint

[oli]

Whilst very much DIY, I had myself down as a a fairly competent sprayer. Nothing fancy, mainly wheels and trim etc but I've done a few touch up jobs and even a whole wing that looks decent even close up, but something is going seriously wrong and it's driving me mad!

I've been painting a winch bumper recently (after eventually removing the powder coating!) it's big and flat and angular, so should be a piece of p*ss, but everything keeps running!

I usually use Halfords paint from their mixing desk, which I know a lot of people don't like but their matches for my Epsom green discos have been perfect. I usually thin them to about 25 seconds through my mixing cup and it seems to spray fine. I presume this is enamel?

I recently tried to spray the bumper (after priming) with an enamel from Spraywell, which seems to have a very good reputation. I was advised to thin with 20% thinners. This seemed very thick through my cup at 40 seconds plus. It seemed to spray ok, but rather spattery, as opposed to misty and if you put enough on for it to go glossy (you know how all the dots suddenly merge and it develops a shine?) it seems to slowly sag and run!

It's also still tacky nearly 18 hours later!

I'm not sure where the problem is and as I'm self taught I'm not really sure what to change first.

Could it be -

Halfords actually isn't simple enamel and I've just become used to something else? Cellulose? (I have sprayed what certainly was enamel, but it was many years ago on an old tractor)

It's far too thick? (I thought things ran less if thicker - though this seems to sag, rather than run as such)

It's too cold? (I'm usually a fair weather sprayer!)

I'm using too low a pressure (about 30psi) or too much feed setting on the gun?

Something I haven't thought of?

Oli

[sorted]

Paint from Halfords for spraying is probably cellulose or acrylic 1 pack rather than enamel.

When it goes on spatters as you describe usually due to being too thick, so you then spray thicker to get it to flow and then too thick and it sags!

If spraying outside in current temperature that won't help either, if possible warm up both the surface and the paint which will help flow.

You haven't ended up with water based have you as used by pro shops? Intended for hvlp guns and must be dried by heat and airflow.

[oli]

It's certainly not water based - it's got that real oily smell you get from enamel paints. You know when you smell a really distinctive smell for the first time in ages - it smelt exactly like the stuff I remember spraying an old Fergie tractor with about seven years ago (which certainly was enamel) which set me wondering about the Halfords stuff.

I think it must be just too thick still. The only other thing I wonder was if I hadn't stirred it enough as I usually use paint soon after it's mixed, whereas this tin might have been sitting on the shelf for a while.

Oli

[magnus]

I only ever had halfords mixed paint in aerosols & it definately smells (& goes on ) like cellulose !
Usually get a decent colour match though !

[oli]

Perhaps I've become used to spraying cellulose then?
I'd assumed cellulose was something historic with painting.

The only reason I didn't this stuff from Halfords was that they couldn't mix me any simple black and told me they needed a paint code to mix ANY sort of colour when I plucked a specific black from the back of my mind.

Oli

[valhalla]

Spraying enamel is very different to spraying cellulose. In this weather, it's an acquired art and a nightmare outdoors, or in an unheated garage. The only way you can make life easier for yourself is to thin it down a bit more, spray it on in light coats and not worry too much about a decent flowed-finish, then when you're happy with the thickness of paint, flow each surface whilst it is horizontal with a final coat. I've struggled in the past with enamels like "Tractol" that the LR indi's used to sell, but you can get a reasonable finish if you're prepared to build the thickness up, then melt the surface with a very thin mix. Otherwise just wait a few weeks and polish the surface back (carefully).

Have you thought about using one of the 2-pack "chassis black" paints that are fairly common in classic restoration circles? I don't think they are quite as bad as the full-blown isocyanates that most 2-packs give off, although they need a little care.

[oli]

"Tractol" that rings a bell. I'm sure that's what I used on the Fergie. Must have been blo*dy lucky with it as I didn't have a water trap, pressure regulator or flow cup. I just vaguely remember thinning it until it looked really runny and spraying away. I suspect being outside in a hot summers day must have helped and the spray bounce must have been horrific at full pressure as I remember my hair feeling like it was covered with hairspray!

I've got some wheels to do now. I'm tempted to go back to cellulose...

Oli