The Spray Painting Thread

[oldcorollas]

hmm, i've been spraying in my hi-tek booth, with loose dirt floor... no dust problems so far.. just insects

did you blow over the area to be painted and surrounds, to make sure there is no dust in crevices that will get blown around by the gun?
did ya wipe it down with prep-sol just before painting? (that seems to get off a lot of my dust )

[o_man_ra23]

I mopped the floor to get it clean. I must say that zero dust issues arose, however due to the evening period that the latter coats were applied, the bugs did find the surface attractive, despite having bombed the shed the night before.

[ian]

spraying the floor with water has no effect on humidity unless its left in there for an extended period
many spray booths have a water circulating under the the floor grills to catch the overspray

[Cuzzo]

hmm, i've been spraying in my hi-tek booth, with loose dirt floor... no dust problems so far.. just insects

did you blow over the area to be painted and surrounds, to make sure there is no dust in crevices that will get blown around by the gun?
did ya wipe it down with prep-sol just before painting? (that seems to get off a lot of my dust )

Yeah I did all that.

[Sirsh]

What are the issues which I'd face if I painted without stripping back to bare metal? Painting with factor colour underneath primer then painting with 2pac paint?

["Z" UTE]

Sirsh, there should be no issues. Just sand the existing colour coat to enable the primer to adhere.


cheers Chuck.

[o_man_ra23]

Sirsh, depends on what the existing paint is like, and what the surface under it is like, as to whether or not you can get away with painting over the existing paint. Once I sanded mine deep enough, I found a lot of very small spiders starting under the paint (corrosion starting from a point then moving outward like spider's legs), which meant that I needed to sand back to metal. If you have the same problem, and paint over it, it will come back. If you don't have issues like this, then what Chuck said is the go.

[Sirsh]

So i have to sand the primer (its dirty as its been in primer for quite a while), and if i see any traces of these 'spiders' take it back to bare metal? how do i know there isnt spiders unless i sand the whole car down to the original paint which would require me sanding the whole car back.

["Z" UTE]

Sirsh, if the car has been in primer for a long time, I would suggest sanding all the primer off. Primer is unfortunately hydroscopic. (ie. it absorbs moisture) Over a prolonged period this moisture will migrate to the bottom of the primer layer, and make contact with any exposed metal, this is where rust starts its cycle. As Owen has mentioned a spider will develop under the paint. It only takes a small stone chip to remove the paint, and phosphate coating on the steel. Bare steel, moisture and oxygen, and the rust trilogy is ready to go.

My advice, is to sand all the primer off and start again. In the areas that are prone to stone chips, leading edge of the bonnet, above the windscreen, front apron, I would probably try for a bare metal rub back, just to ensure you have no problems in the future. With the rest of the car, you will get a good feel for the condition of the original paint as you expose this layer by sanding, if the paint is in fairly good unbroken condition, just re prime, guide coat, sand, fix imperfections, spot prime, and then lay on some colour.

cheers Chuck.

[o_man_ra23]

Chuck, add to that list the rocker sills, rear qtrs, around wheel arches, bottoms of the doors, back of the door jambs...

[oldcorollas]

Sirsh, if the car has been in primer for a long time, I would suggest sanding all the primer off. Primer is unfortunately hydroscopic. (ie. it absorbs moisture) Over a prolonged period this moisture will migrate to the bottom of the primer layer, and make contact with any exposed metal, this is where rust starts its cycle. As Owen has mentioned a spider will develop under the paint. It only takes a small stone chip to remove the paint, and phosphate coating on the steel. Bare steel, moisture and oxygen, and the rust trilogy is ready to go.

Chuck, how does that sit with wet sanding of primer, prior to colour coating?
if the primer absorbs water, then wet sanding primer should be a huge no-no?

["Z" UTE]

oldcoroola's, I understand how you would think that. However, it is the prolonged exposure to the daily temperature cycles that draws the moisture way down to the metal. Wet sanding will have nil effect.


cheers Chuck.

[mscphillips]

Hi Guys

I noticed there is a fair bit of painting expertise floating about this thread!!

i am currantly respraying my ra23 my question is

i have primed it and blocked all large areas with large bloakc and 240grit, what is the best way to do the door jams etc, can i just leave the primer how it came of the gun or do i need to rub it back, if so what is the easiest. scotchbrite? 240?

thanks

craig

["Z" UTE]

Craig, first up you need to re sand with 600/800 before you apply the colour. 240 is quite coarse, and will result in scratch marks showing through the colour. The red scotchbrite starts off fairly agressive, but quickly breaks down to a finer grade, so that should be fine for doing the door jambs etc.

You must sand the primer to remove the extreme top layer to provide a good base for the colour to "key" to.

You can apply colour to very fresh primer without sanding, by very fresh I mean is has been on the panel for no more than a couple of hours. What happens in this case, is that the colour and thinners will "melt" the primer slightly and the two paints will bond together. This will not happen with one week old primer.

cheers Chuck.

[mscphillips]

Thanks for the reply chuck

is that 600-800 dry or wet and dry?

what about buzzing over large areas with the orbital sander and a soft pad?