Any spray painter gurus? Painted roof white. Dull patches.

[spudboy]

Spent the day sanding, masking, priming and painting the roof of one of my cars white today (I do love a white roof!). Well, 'Chawton White', which is a TD5 type of white.

Anyway, it got 3 or 4 coats of Dupont Acrylic 400, thinned 50:50 with the proper thinners. Left 10 mins between coats to flash off.

I now have quite a nice finish, but the gloss is a bit patchy. The final area sprayed looks excellent, but the earlier areas I sprayed seems to have got overspray on it and have dulled off. The vertical bits all look pretty good but the dulling off is most pronounced on the flat roof top.

Is this normal, and I just need to wait for it to harden and then polish it with a paste or something?

Temperature was in the low 30's, if that is relevant, and very low humidity (this is Adelaide...).

Any thoughts?

Thanks
David

[Hoges]

once the top coat is hardened, you can then get a gloss finish by hand rubbing it down with 2500 wet and dry paper which has been soaked in water for a few hours before hand and using a slow running hose to keep it wet. This will bring up a good gloss finish. If you do a net search on finishing /detailing etc there's a lot of good info on how to complete the task. Good luck with it!

[spudboy]

OK - thanks for that. I'll go and chase down some 2500 paper.

Can you spray a clearcoat over acrylic to get a gloss, or is that only for 2 pack? Or is 2500 wet and dry the final step?

[jerryd]

Isn't 50/50 a bit too much thinners :confused: I just painted juddy's car and we used 5 parts paint to one part thinners, the final coat was as wet as i could put it on without it running. This was enamel paint in army colour.

[spudboy]

That's what I thought too, but that was the instruction on the label. 1:1 for solid colours an even more thinners for metallics :eek:

[B92 8NW]

That's what I thought too, but that was the instruction on the label. 1:1 for solid colours an even more thinners for metallics :eek:

Lucite 400?

[spudboy]

Yep Lucite 400.

Don't tell me I have mis-read the thinning ratio!!

I am going out to the shed to read it again.....

[Judo]

Years ago when I sprayed a few panels I remember thinking 50:50 was a huge amount of thinners as well - but 50:50 sounds about what I did as well. I'm sure you could go a bit less and it would be OK, however it's because it's so thin that you get the glossy finish. It's a very fine line between getting it to pool on the surface to create the gloss and spraying too heavy and having it run.

Did you do much "test spraying" before the roof? I'm no expert, but in my experience if you don't get the spray just right - heavy enough to (ever so slightly) pool on the surface - it won't gloss over. Could it be just uneven spray?

[Judo]

^^ "pool" sounds like the wrong word, but I guess you know what I mean. All the drops from the spray need to join to form a smooth surface. If they don't, it can leave a matt appearance.

[rocket scientist]

Just painted my county with Northane Polyurethane.
Great gloss finish, and tough as nails.

[spudboy]

I did a bit of testing first to play with the air and feed controls.

I was using a deVilbiss (?) gravity feed gun at 25PSI.

First coat went on nicely. Did the 2nd coat 10 minutes later and it was a bit gluggy to start with, so must have settled in the pot a bit. Came good after a few dummy sprays, but was never as nice a coating as the initial one.

It just seemed that I could lay it down smoothly on one side, but when I switched sides, it lost the gloss it originally had with the overspray from the other side. Does that make sense? It seemed to dull off with the overspray landing on it.

[spudboy]

Just painted my county with Northane Polyurethane.
Great gloss finish, and tough as nails.

Just Googling Northane Polyurethane.

2 pack paint. Looks more complicated than acrylic.....

[Judo]

You mean you stopped half way across the roof, then started again on the other side? I was always under the impression you had to do a full sweep. That could be the problem... Although I can see the issue with the roof. :eek:

[spudboy]

Yep - that's right. Did one side (half way). Then had to go around the other side and do the other half. Couldn't reach right across the roof to do it all in one pass - arms not long enough!

[rocket scientist]

Just Googling Northane Polyurethane.

2 pack paint. Looks more complicated than acrylic.....

Easy to mix, 2:1.
I used the Ship Shape primer (3:1)as recommended, sticks to anything.

You do need to spray within 3-4 hours of mixing before it starts to go off.
And of course wear a decent mask, preferably full face. This stuff is not good for you lungs!

[isuzurover]

People are comparing acrylic, enamel and 2-pack paint in this thread. They are all completely different - and thinning ratios are not the same. e.g. you can spray some 2-packs without thinners.

Also - enamel and 2-pack will (should) be glossy straight away. Acrylic needs to be rubbed back and polished as mentioned.

[Baggy]

Hi Spudboy,

You only use a clear over metallic paint
Paint needs to be runny and the advantage with acrylic it goes on wet and dries almost immediately.
I believe your spray pressure is too low and the paint may have still been too thick.
When you take into account that at 25psi in the tank the pressure you loose by the time it gets to the gun you would be lucky to be spraying with 15psi thats why its probably spraying dry . I'd be running my compressor at 100psi minimum. Also check air hole in gun lid is not blocked as tipping gun forward to spray with a full pot of paint can block hole and that can effect spray.

If you have some reasonable coats as someone suggest rub it back with 2500
wet & dry paper using a cork block and a bucket of soapy water to remove the overspray from the surface.
Once done you will need to buy or hire a proper polisher that has variable speed control. There are a number of polishes available that go from course cutting compounds to mirror shine through a stepped process.

Nothing wrong with spraying half the roof at a time as it is a bit of a stretch, but I'd do say 1/4 LH Side and then do R H Side then back to LH Side until it's finished. You can on the next pass spray in the other direction across roof.

Personally unless you have a proper spray booth, quality mask etc etc I'd keep well away from two pack paint - it dangerous stuff.
Must be at least 20 years ago my brother worked for a major automotive paint company when they brought in two pack paints.
I recall the spray painters spray suits and masks they used back then were air pressurized to stop any possible contact with fumes and paint :(

Cheers

Baggy

[spudboy]

Thanks Baggy - that's a lot of good info there. Looks like I need to monitor my pressure at the gun. The data sheet for the paint specified 25PSI at the gun, but I had 25PSI at my compressor regulator.

I stayed up late last night watching YouTube videos on spray painting & prep. Even found a good video where a bloke painted the top half/bottom half of the same panel with acrylic and 2-pack as an example of the difference. He was pushing the 2 pack route, so that seems to be the preferred route if you've got the gear. He hired out a spray booth at a local body repair shop.

Seems I need to get a pressure gauge for the bottom of the gun, and a filter/drier to screw on the bottom of the gun. The guy in the video had a little blue filter/pressure gauge unit that looked very neat.

This is the link to the vid BTW, a good watch: 1K Acrylic VS 2 Pack Auto Paint + Dent Repair - YouTube

[Scouse]

You only use a clear over metallic paintClear can be over any sort of paint, metallic or solid.

As stated above, different paints have different thinning requirements which is why acrylic needs several coats to build up coverage whereas enamel/2k just needs a couple to provide coverage.

[dullbird]

Spudboy I have only spray paint 3 times.....so Im in the same boat as you..

one thing I did do though is the first time I sprayed Ian set the compressor to the pressure and the paint went on patchy (not shockingly) especially as there were moments of pressure drop while the compressor went Oh I need to kick in.

then Ian got me a pressure regulator for the spray gun itself....

I sprayed my rock sliders with this and Im pretty sure the gauge was set to 45psi (dont quote me on that though play with your own pressures see what works) and I can tell you the difference in spray was amazing!... the paint went on very very evenly.

so having a regulator and gauge on the gun I would say is a must..mine too is a gravity feed gun.

[Tank]

Spud, the best way to sray a roof is to have 2 painters or have milk crates either side with planks between so as you can get up and over the roof so as you are not spraying close to horizontal.
What I do is set the planks up so that i can get to the other side of the car quickly, without falling arse over or getting the air line tangled up.
Then I spray from the gutter rail out towards the centre, keeping the gun pointing down and not out away from your body, when I get to the centre or the limit of my reach I spray a fairly wet pass and then race like a ratbag around to the other side and commence sraying where I left off and back towards yourself. Takes some practise to be able to get around the vehicle quick enough, but I have found it eliminates most overspray, Regards Frank.

[460cixy]

You need to cut back acrylic paint it will never shine off the gun and will normally have a textured finish. Get your self some cutting compound and some proper open weave polishing cloth get both of these from the paint supplier don't be tempted to use an electric buff . When. You are happy with the finish from cutting it back get your hands on some corn flour. Throw it over the surface and use the same type of polishing cloth and polish it with the corn flour you should and up with a finish smooth as glass and good shine. NB. Be carefull cutting on edges as the paints thinner and will rub clean throu the new paint

[Hoges]

Be careful which cutting compound you buy... some are quite harsh. The cornflower hint is a great one. Properly done you can get a "concours" standard finish. Suggest you also hunt up the 3M website and take a good look at their 'system' for producing a professional finish. They cater well for the DIY brigade... Also search youtube and hotrod web.sites I got a lot of practical stuff from Youtube (picture worth a thousand words and all that:D) as well as some of the US hotrod detailing sites...

[460cixy]

The paint supply joint should point you in the right direction on what compound is best. We used to use run of the mil off the shelf stuff but if its your first go at it go for something fine

[Baggy]

Thanks Spudboy,

The video you posted was very informative and as everyone else has said there's a lot out there to help you.
That blue filter is a neat addition and I may look at one although I do have filters fitted to the hose lines :D

Yes, Scouse is correct that clear can be put on all finishes, but its not normally used when spraying solid acrylic colours.

As Dullbird mentioned keep an eye on he PSI as that will effect the paint finish as if it drops too low, the time it takes compressor to kick in again can effect paint.
I run higher pressure as I have some fairly long hoses to get around vehicles and concerns of the drop in pressure as you are spraying.

Tanks advise on planks and someone to help is invaluable and worth serious consideration as having an extra hand to hand you the gun (while getting up), moving the hose and topping up gun without getting up and down is a bonus.

I resprayed my RRC 2 Door last year on a whim, by that I 've had the paint for at least 5 years but like everyone life's busy.
I wanted to smarten it up as I had undercoated the bonnet, door and guard and it was looking a bit ordinary.

I did no filling, just rub down the body , etched primed as necessary and painted it under an open lean too at a factory with a 25km wind on a fairly cool day for Perth with a faulty spray gun I had to change over halfway through .........all the wrong conditions for spraying :o
(My brothers shed we normally respray cars is full with unfinished projects at the moment so unavailable)

Amazingly its turned out great under the circumstances, and I'll post a few photo's for you to see.

Good luck with the roof,

Cheers

Baggy

[Baggy]

Hi All,

Some photo"s of my respray job on RRC 2 Door,

She"s a continuous work in progress :D

Cheers

Baggy

[spudboy]

To sort out air pressure at the gun, I got one of these today. Was about $25:
https://www.aulro.com/afvb/images/imported/2013/01/111.jpg (http://www.google.com.au/url'sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=9uCjCYZO85ghPM&tbnid=HRqhoN263Ka8pM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.ebay.com%2Fitm%2FHVLP-Spray-Gun-AIR-REGULATOR-PRESSURE-GAUGE-Auto-Paint-%2F190782600394%3Fpt%3DMotors_Automotive_Tools%26h ash%3Ditem2c6b8774ca%26vxp%3Dmtr&ei=N64HUe7kLeiKmwXxtYDYCA&bvm=bv.41524429,d.dGY&psig=AFQjCNEPlaLXWYJVqgCeKppAnR1NK5cPeA&ust=1359544248149461)

Just attaches to the bottom of the gun.

http://www.mactools.com/Portals/1/aspdnsf/images/PRODUCT/medium/AR981.jpg

[Shiftit]

Base coat is usually 1:1 50/50 once flashed of it usually goes a bit dull and can sometimes go patchy, but when you add the lacquer it pops!

Lacquer is mixed at 2:1 (hardener) with 10-20% thinners.

Solids ( one coat ) are also mixed at 2:1 and dependent on temprature usually require between 10-20% thinner also.

generaly the hotter it is the more thinner you add.

Hope this helps.:)

[mike 90 RR]

Left 10 mins between coats to flash off.

The problem with areas such as roofs is the over-spray settles on it ... Try wiping the area with a "tack rag" to remove the over-spray dust, prior to applying the next coat ...

Cheers
Mike

[Judo]

Now we just needs pics of the offending roof. ;)

[ScottW]

If you have some reasonable coats as someone suggest rub it back with 2500
wet & dry paper using a cork block and a bucket of soapy water to remove the overspray from the surface.

This makes a difference. It keeps the paper from clogging up as much. If you don't pay attention, the clogs may scratch the paint you are trying to fix.