The Spray Painting Thread

["Z" UTE]

Bad preparation, some corrosion has been left untreated. The expanding corrosive mass has fractured the bog and paint, allowing moisture to penetrate both the bog and the paint and give the corrosion a real kick along. You will have to remove that ugly scar, right the way back to bare metal. Treat the metal with rust converter, prime, bog and repaint. The paint looks like acrylic, but can not really say for sure.

If the substrate in that hole is soft, it may have been an incorrectly mixed batch of bog or hi fill primer.


taff, do you have fruit bats in your area or where the car came from. Their droppings have a mean high acid content that will eat through paint inside 24 hours.


cheers Chuck.

[Z2TT]

Hi Chuck,

So speaking about using the 1.7mm Tip.

So instead of using my primer without any thinners as directed by the paint shop, should I add about 10-20% Thinners to it?

As for the paint you said to thin it more than usual, so instead of 50% Thinners like you recommend should I use 60%? or stick with 50%?

["Z" UTE]

Z2TT, yeah thin the primer to allow it to flow through the gun tip, otherwise it will be like sandpaper as big gobs of paint are forced outa the nozzle. BUT for the top coat you may have to reduce the thinners ( I will go back and hi lite that in my previous reply) or reduce the flow from the gun, it has the potential to be run city using too large a tip.

cheers Chuck.

[SHEPPO3930]

Hi guys,

I want to buy a cheap spray gun to paint my car in primer/filler (Concept paints acrylic primer filler). What would be a good bang for buck gun? And what size tips do i need to get? Ideally I'm after something available from a mainstream shop like supercheap/autobarn/bunnings, etc, as i'd like to purchase it in the next couple days. The top coats will be applied by a mate in his booth with a good gun, but i'm doing all the prep work and want a cheap gun to get me through the job.

Cheers.

[kremsra28]

i have a workquip pack for my primer, can get them for around $99 at rare spares (our local is combined with paint and parts so might not be in a rare spares only shop), comes in a kit, 1 gun but comes with 1.8mm and 1.4mm tip setups, seems to spray primer well, havent done any base or clears with it, but should be ok, also try a velocity gun, they seem to be pretty good for the money, start from around $110 upwards. they too are at our rare spares, i havent shopped at supercheap for guns, i have bought some other air tools and they seem pretty good, my palm nailer, d/a sander and air chisel gun, just dont get a hvlp gun tho, the cheaper 1's wouldn be much chop, and they would need a pretty huge compressor to run them.
krem

[Taff]

taff, do you have fruit bats in your area or where the car came from. Their droppings have a mean high acid content that will eat through paint inside 24 hours.


cheers Chuck.

This may be it. Its the only spot on the car which had any paint issue. theres rust here and there but the paint seems pretty good quality.

Is there an easy way to tell what type of paint it is?

Also i would love some tips for sanding bog near sharp corners. There must be a trick to it... i am still learning and i just cant seem to stop rubbing through.

["Z" UTE]

Long distance identification of paint is not a great idea, take it to a panel shop and ask the painter what it is, and how much it is going to cost to fix. the idea of quoting work for a dollar will get them out to the car

As for breaking through your paint adjacent to new bog when sanding, well that is always going to happen. To minimise the damage make sure you always use a ridgid sanding block, and just take a bit more care around the edges. That feathering is not such a bad thing if controlled, as it will give a nice surface for the primer to bond to. You will always end up painting at 15 to 20% more of the car than just the applied bog, it is the nature of things with bog and paint.

cheers Chuck.

[Taff]

thanks again.

Will keep trying until i get it right.

[o_man_ra23]

As for a cheap gun, the $40 superthief HVLP gun I bought (was on special at the time) worked fine for primer, as did the $80 tradequip unit (which came with a 1.4 and a 1.8). Have used both for topcoat (acrylic only with the superthief gun, but did some enamel and some 2k with the tradequip), and they didn't do too bad, wouldn't use them for topcoat on anything too special though.

[1JZ-Rolla]

So I had a bit of a fkup today, painting some plastic trim panels for the car.

Had previously rubbed them back (last week), light coat of plastic adhesion primer, then coats of an acrylic pressure pack primer suitable for most top coats. blocked back the primer, washed, and then top coated this afternoon with solid black 2k.

Was 21 degrees C, Laid the topcoat with a light adhesion coat to begin with, flashed off 6 minutes as per instructions before a medium wet coat, then finally a full wet coat. Flowed off the gun really nicely, and after flashing off the final time had a great gloss and no dry spots or nasty orange peel, just a bit of dust naturally.

Anyways, after about 30 minutes, these bubbles started to happen:






Reckon I was too hasty to lay each coat without letting the paint flash-off properly, or is it more likely that the final coat was just too heavy? The raised spots appear to be a solvent release problem.


Cheers

["Z" UTE]

Phil, that was some nice work, yes you are corect the bubbles look like entrapped solvent doing its damdest to get free. Probably as you say a little hasty to get the coats on. Nothing for it but to let it cure then have another go after sanding big time.

In my personal experience I will never use any pressure pack products under gun applied paint of any description. I had to repaint an RA28 becuase the spot primer from a pressure pack reacted with the colour coats!

cheers Chuck.

[1JZ-Rolla]

bugger....... and this primer was recommended by the paint shop too for its compatability......... was trying to avoid over complicating the job with only such a small area to paint, hardly seemed worth mixing up primer etc. Lesson learned.

[Taff]

ok so after a fair bit of reading I just want to make sure this is right for respraying my ra28

- Mask up
- Sand back with orbital sander (180 grit?)
- wax and grease remover
- Spray putty (do i need to prime first?)
- Guide coat and sanding (360-480?) to make it nice and flat
- wax and grease remover
- Primer
- leave for a week?
- wax and grease remover
- colour - 2 wet coats then a few light coats (can be done on the same day?)
- wax and grease remover
- clearcoat, 3 coats?
- cut and polish

The doors / bonnet / guards are off the car at the moment. should i paint the door jambs and undersides then put them on and paint the whole car at once or paint them separately?

Going to use acrylic and doing it in a pretty clean garage. Have a good compressor/gun.

Thanks.

["Z" UTE]

Taff, why mask before sanding? You have to apply masking tape just prior to painting, and remove the tape as soon as the paint has flashed off. Why leave the primer for a week? if you have applied it correctly, there will be no gains to be had leaving it that length of time.

My process is as follows,

Wash the car to remove all traces of wax, oil, and grease, I use sugar soap and hot water for this.

Sand with, and this is where it gets tricky, if the paint is in good condition, use 600-800 wet, if the existing paint is real bad knock it back with 60,80,120 dry.

Wash again with sugar soap and hot water, dry off then mask.

Prepwash, then apply as many coats of primer filler as you wish.

Guide coat and sand back with 240 dry, remember the finer the grade of paper at this stage, the less chance of sanding marks. Remove the masking tape at the critical edges and ensure you have had no bleed through. This sanding step can take as long as you need.

The next steps can and should be accomplished in the same day.
Apply new masking tape. Prepwash and dry off, apply primer, then as soon as that flashes off, apply a light coat of colour followed by a couple of heavy coats of colour, observing flash off times between coats. Apply a couple of heavy coats of clear, then a light ultra thinned coat of clear, ie. 20%paint 80% thinners, this final coat will level all the paint, and give you a reasonable gloss "off the gun".

My idea of a heavy coat is just enough paint so that it does not run, and each pass of the gun should overlap the preceeding pass by 50%, again not so much paint as to cause runs, or sags.

The car should be assembled for final colour coat, or at a minimum the panels should be hung in the orientation that they will be when fitted to the car. Paint lays differently on vertical and horizontal surfaces. If you laid a door flat and painted it, the finish will be slighly off from the rear qtr. Not ultra important with monotone colours but anything with a metallic or pearl in it will show up big time.

Let the car sit for 3-7 days for the paint to cure, if you can and weather permits park the car in the sun, the UV helps to cure the paint.

Before cut and polish, give the car a complete rub over with 2000 wet using soapy water, this flattens out the orange peel and will help to really gloss up the paint when you cut and polish it and give it a coat of wax.

cheers Chuck.

[Taff]

Taff, why mask before sanding? You have to apply masking tape just prior to painting, and remove the tape as soon as the paint has flashed off. Why leave the primer for a week? if you have applied it correctly, there will be no gains to be had leaving it that length of time.

I read somewhere (i think this thread actually) that the primer shrinks as it dries and it needs to be left for a while to stop crows feet?
As for the tape ignore that bit

You are a massive help. Do you use a certain type of paper for dry sanding?