FE-FC Holden Discussion Forum

Now that I have finished(?) the painting the ute can anyone offer some tips on spraying acrylic?  ::)

I think I had the pressure too high as the gun was spraying paint, but it was also shooting off little semi-dry strands of paint that have given the paint a rough texture. Less pressure 20 psi and thinner paint seemed to help with this. I was using a "cheapie" $85 gun with the pot underneath.

Secondly, how long should I wait before colour sanding and polishing? I had a go at my test panel 1/2 hour after, but I want to play safe with the car itself.

tips-
if the paint is to thick it will come out stringy, I start by mixing 60% thinners, 40% paint and get thinner at the end like around 35 paint and 65 thinners, I also use 2k thinners in the final coat wich lets it flaten out better on the panel.
When you do the first coat dont try to cover the primer, make it light.
after the first couple of coats you should be laying it down nice and wet, but without running.
start the roof from the side and then go around the other side and start in the centre of the roof so you meet up with the wettest paint.

Wow, thanks Leon, I thought I was pushing the envelope at a 80/20 paint to thinners :o
Live and learn ::)

Hi Stinky
Have also just bought some acrlyic myself (also very green) & label says to mix 100 parts paint to 150 parts thinners, ie 40 paint - 60 thinners, 1.8mm neddle, suction gun pressure 2-4 bar (30 - 50 psi), leave 3-4 days & sand with 1200 wet dry, but as always these numbers will vary according to tempureature, gun & painter technique etc.
They suggest leave paint to for round 4-6 weeks before buffing/polishing

Cheers

Thanks guys, I now have full 20/20 hindsight

HI Glenn

The longer you let the paint go off the better. My suggestion is to block it back flat just before you want to buff it as if you block back, lets say in 2 weeks and buff in 6 your paint has had 4 weeks to shrink more, therefore harder to get a flat glass finish as you will get shrink back. I suggest leave it as long as possible before you slice and buff.

The other suggestion I have is when you are spraying in the door jams, dash ect, where it is near impossible to buff  put 20% paint, 20% good clear and 40% thinners or a bit more thinners if you want it to go on really wet and flat, use this method towards the end of your spray job and done right it will be like glass in there.

Regards

Julius

20% clear and 20% colour and 40% thinners may give a cobweb effect out of the gun. maybe you could use coluor followed by a mix of clear and colour in the last 2 coats with 2k retarded thinners, door jambs are tricky becuase you want the best gloss of the gun to cut down on tricky and risky buffing but you can hand compound them, I am thinking of doing my door jambs in 2k like my engine bay.
I am a detailer not a painter and maybe some one like Alfio, aka the love god could give better advice.

As for buffing I have done this a few times 24 hrs after the paint went on. If you do, dont slice it right down as you will want to buff it again 6 weeks later, in that time you will get shrinks and sinks showing and the paint will dull a little as the solvent evaporate, then in 5 or 6 weeks slice it  and squeegy it if you want a better shine, squeegy till the hole surface looks matt with no shinny dots and then buff it with green compound and sheepskin followed by a lighter compound and polish.

Hi Guys

Sorry I meant 60% thinners and not 40% to give a 100%. Thanks for picking up my mathematical error.

Julius

Rub down in progress, 2nd paint session this weekend  ::)

Thanks again, and I'll offer a tid-bit in return.

If your paint shop doesn't stock those plastic lid pourers (or you are too cheap  ;D ), cut the side off of an icecream container and shape to suit. The folded lip at the top of the container fits perfectly into the groove on the paint tin for minimal mess when pouring.

Just curious as to why I shouldn't do this to the main top coat on the rest of the car?

The reason why, is that your not going to slice those areas back  the only thing you may do is hand buff these areas thus no chanch off slicing through the clear coat colour mixture.

If you do that to the exterior which your are going to slice back and buff you may cut through the clear coat in places and when you buff it you will have different shines and textures.

Hope this explanation helped

Regards

Julius

Thanks for all of that, we'll see what happens this weekend  ::)

Hi Julius
Have taken onboard your advise to Stinky & tried 'dry run' on an old bonnet with a suction gun but wondering if a gravity gun would be better & if so what size needle - would 1.4mm be ok for acrylic

don't mean to hijack ya thread Stinky, just a good opportunity to ask a question

Cheers

That's not hijacking blue, it's when people change the subject. It's good to get a few opinions and other questions. Usually if one person is asking a question there are 50 others who are thinking it.

I use a gravity feed gun with an acrylic nozelle dont ask what size I dont know. I find it easier to use a gravity feed as I dont bump the pot on the job.

regards

Julius

Thanks to all, especially Leon and Julius.
The second run at the paint went better, we won't win any best paint trophies, but we should have a car that we are not embarrassed to drive down the road.

My tip - pay the extra and get a gravity feed gun, after a few bumps and anxious moments getting into spots with the suction gun (pot on the bottom).

I'm glad it all went well. If you put a few extra coats on you can make an Ok job into a fantastically flat job because you know you have plenty of paint to work with on the job.

Remember when slicing back don't slice to much on edges because when you run the buff over a guard for eg, you will tend to polish over the head light ridge and if you have sliced it back flat your going to buff through it.

If you want me to explain this in more detail or you may have a question just ring me on 0407486759.

Regards

Julius

I thought of that and put a little extra on the edges and ridges in anticipation. I should have plenty of paint on there now as I bought 4 litres with 1 litre thrown in, then got another 2 litres after the initial stuff up.
I probably have a litre and a half for the tailgate and bonnet (next weekend  ::) )

Three other points for any beginners using this thread for reference.

1. Grab paper cone filters from the paint store, mix your paint in a seperate container then pour through the filter into your pot. You'd be amazed at the amount of crud that comes out.
2. Get a good spray painting face mask.
3. Don't eat anything spicy before starting painting, once you get that mask on, poooeee  ;D

How big should the spray fan coming out of the gun be? and what PSI should I be running out of the water trap?

I had the water trap set to 30PSI, the spary fan would have been 5cm tall by 2cm wide. Detail areas around head and taillights came up a treat, but the larger panels look streaky and dry as it was harder to get a good overlap. I am guessing I either need more practise or some settings are out :'(.

Hi Stinky,

I've only just read this thread.  I have a mate who is a spray painter and he says all the old guys at work say that when you mix your paint and thinners (with a steel ruler), you should pull it out and get about 7 quick drips in a row - thats when you can tell you have an ok mixture.

He sprayed about 5 coats of 50 thinners/50 paint, then 3 coats of 70 thinners/30 paint on a guard for me and it came up a treat.

Gravity fed is a must.  With pressure, it depends on the gun as well.  Some guns also have a pressure gauge.

He wasn't too concerned about pressure with acrylic - I could ask him if you like?

We sprayed a tailgate with what he called a touch up gun and it came up well.

Dave

I have been using a "pot-under-gun" setup, because it was cheap and I don't paint all that often. I also bought a gravity fed touch up gun yesterday with a view to painting smaller parts, I might even try it on the yet to be repaired tailgate and bonnet.

The dry areas did come up ok after a bit of sanding, but I would prefer the gloss I got in the smaller sections to be all over the car.

we run 60 psi at the water trap, with a gravity gun and this gives a really nice smoothe finish, with little to no orange peel. gravity guns are the go! i saw a pair at super cheap (i think one was low pressure, for primer filler/putty).

we ordered one from our paint supplier, cost around the $220 mark , i think the brand was devilbliss (or something similar) this is the gun we have been using for the past couple of years. the only problem the gun has ever had is the little breather hole on the top getting clogged from the gun getting put on weird angles to paint things like sills.

hopefully that might help..

If your original problem was paint going on very dry, apart from thinners another factor could be that the air temp was too high?
I sprayed once on a 28 deg. day and the paint dried before it hit the job and gave a good sandpaper finish!
Also your spray pattern of 5cm X 2cm doesn't sound right, I would have thought a longer, thinner fan pattern would be better.
300psi also sounds very high.Try using the minimum pressure that still sprays a good pattern. Just keep dropping the pressure and testing till you reach the right point. Too high a pressure just puts paint into the air and less  where you want it!

PS. Don't take anything I've said here as gospel, as it's just some points that I've learnt by trial and error ::)