The Spray Painting Thread

[Sigmeister]

Long thread, be patient. I will update with progress and pitfalls.

OK, so there are a few threads around regarding spray painting. I was hoping to get as much info together into one thread.

I am currently a noob and would like to learn the in's and out's of everything from body prep to painting. So I have got myself something to practice on.
Exhibit A:



This is the bootlid of my daily (Yes, I actually drive it!). I am looking to restore it to its origional colour. However, because I do drive it, I got another boot lid and will fix that one instead.
Exhibit B:


OK, now for your turn to help. I have a lot of questions so bare with me.
Question the First:
What should I use to remove the old paint? I would like to avoid a chemical stripper, so would something like this do?


OR this:



The second one seems pretty harsh for sheets. The first one is good, I gave it a go but noticed it heats up pretty quick. So do you just take it easy? Or are there alternatives?

Question the Second:
The bootlid near the lock has a few little holes that need fixing as can be seen here:


Would it be best to weld these up, or use like a thick fibreglass type bog?

Question the third:
In the picture you can see there are some cavities and nooks and crannies that I won't be able to get into:

Do you just not worry about that as when you spray it's going to cover it anyways?

And Finally. Gun choice.
From what I have read, I need a HVLP gravity fed gun. This is fine, but when I went looking for one today, the guy was asking which Nozzle size I would need. I had no idea. What would you guys recommend? I will be spraying primer, paint and clear coat. I will be spraying at home so what type of paint would be best for this situation, 2Pack or Acrylic?

Sorry for all teh questions, but hopefully this can be a base for everyone to learn from.
Any and all help is most appreciated.

[GtiRboy]

subscribessssss

[Julz01]

to remove paint Defiantly do not use the wire brush as it will scratch the shit out of the metal while removing the paint.

The first pad inst to bad but still might be to harsh to use. I Normally just use a heavier grade wet and dry sand paper.

As for the holes just use bog on them, way to small to bother welding up

[ian]

go for the acrylic option
it dries quicker and it is more forgiving and about half the cost
i would advise against the wire brush to remove paint
also i would advise against a bare metal sripback
you can block the lid back with 240 wetand dry
use a highfill primersealer and rub that back untill smooth
the good thing about acrylic is that if you have a rub through , it is easy to fix , the rest of the car is in acrylic, and if you do just the boot lid in 2 pac, it will stand out like dogs balls
ian

[Sigmeister]

OK, so turf the wire wheel and possibly that other thing.

Go with Acryic.

Sand with heavy grit wet\dry seems to be the go.

Any reason when not to go to bare betal? Other than perhaps ease?

Oh and for the high build primer, any idea what size nozzle I would need for that?

[timbosaurus]

Hey Mate!

I'm not a proffesional, so don't take this advice as if I was. What I am is a backyarder with a fair bit of patience and willingness to learn. Often DIY like this results in a better finish than a proffesional. Not because of skill, but because of care, patience, time that a paid proffesional cannot afford to spend.

What should I use to remove the old paint? I would like to avoid a chemical stripper,

Why would you like to avoid chemical stripper? The mess? the fumes?

Unfortunately it is probably the best option.

You ahould use an abrasive disc on a grinder to take 10mm back to bare metal all the way around the edges. Then use decent quality paint stripper to remove the rest. You can speed up the process with heat, more stripper, and covering the stripper in glad wrap while it reacts.

The second one seems pretty harsh for sheets. The first one is good, I gave it a go but noticed it heats up pretty quick. So do you just take it easy? Or are there alternatives?

Unfortunately that is the problem with these. The heat can warp the panels. Not to mention the dust, the noise, etc...

Unfortunately I haven't used these abrasive pads on big panels, so cant really talk from experience.

The bootlid near the lock has a few little holes that need fixing as can be seen here:
Would it be best to weld these up, or use like a thick fibreglass type bog?

Yes, weld would definately be the best. It depends on what sort of job you plan on doing though.

Quick, nasty, sell in two weeks:
adhesive patch on the inside, bog over the top. Believe or not, bog is often strong enough to not crack!

Easy, long lasting, and semi-unnoticeable.
put a brass plate up tight behind the panel, use a MIG to weld the hole closed and grind the surface down smooth. Hey presto, weld doesn't stick to brass, so it pops off the back and you're left with a filled hole The welding will have warped the panel a tad, so a quick beat with the hammer and dolley and a quick swip of filler and ur done!

Little more challenging, not very time-efficient but gives a concourse finish.
Fill the hole using the same process but use oxy-acetylene welding instead of MIG. The advantage with this is that you are actually filling the hole with the same metal as the panel. You will find with MIG that the weld is much stronger than the panel so if you plan on massaging the metal, it will be like working with chalk and cheese. Trying to beat two dissimilar metals smooth is a nightmare, as well as being visibly different before painting. Once you have finished oxy-ing, you can beat the area smooth, and file-finish the hole. A proficient welder/beating will be able to make it look like there was never a hole there.

In the picture you can see there are some cavities and nooks and crannies that I won't be able to get intoo you just not worry about that as when you spray it's going to cover it anyways?

Once again, depends on the quality of job. If you want an immaculate bare metal job, you will probably need to dip the panel to get that paint off. afterwards you would thoroughly coat it with deoxidation agent, then spray comprehensively.

If you are just doing a job for a daily, wash it thoroughly with soapy water and prepwash, then spray over the top.

From what I have read, I need a HVLP gravity fed gun. This is fine, but when I went looking for one today, the guy was asking which Nozzle size I would need. I had no idea. What would you guys recommend?

Buy an HVLP gun if your compressor can handle it. They have a much better paint transfer efficiency due to the lower pressure, so will save you a few bucks in paint.

Also see if you can get a gravity feed gun too. I find them easier (less clumsy) to work with and less trouble too. Just gotta have a hook to hang the bloody thing

Regarding nozzle size, you should match it to the viscosity of the media you are spraying. Spray putty is thicker so requires a larger nozzle. Your final coat of acrylic will be quite thinned down, so will need a smaller nozzle.

I will be spraying primer, paint and clear coat. I will be spraying at home so what type of paint would be best for this situation, 2Pack or Acrylic?

For a concourse job, just try to match the original paint type, whatever that may be (usually pre 90's was acrylic). For a nice job, use two pack.

Acrylic requires a lot of post-painting work to bring up the gloss, two pack doesnt. Two pack is tougher too. The down side is that it really should be cured in a booth at a fixed temperature, but both types of paint have been succesfully used in backyards. As long as you are precautious, patient and pedantic!

Tips:

* never spray in an arc. Keep the gun perpendicular to the panel AT ALL TIMES!
*Use about a 50% overlap between lines.
*try adjusting fan width, air pressure and paint volume. More is not always better!

[TC1600]

Subscribed...

Acrylic is much more user friendly for the novice, 2 pack is more fiddly, and i would recommend breathing apparatus also.

And don't paint in 35+ degree heat, I found out the hard way the paint dries before it hits the panel, and leaves a shitty rough finish, which is a bitch to rub back to smooth

[Sigmeister]

This is all brilliant info guys, keep it coming.

Hey Mate!

I'm not a proffesional, so don't take this advice as if I was. What I am is a backyarder with a fair bit of patience and willingness to learn. Often DIY like this results in a better finish than a proffesional. Not because of skill, but because of care, patience, time that a paid proffesional cannot afford to spend.

That's the reason I am getting into it. I can do a bit with electronics and interiors, but paint and panel is something I have avoided. But I figured I'll make a start and hopefully get plenty of Practice in before I do the Celica. I am pretty festidious, so hopefully this will work in my favour with this kind of work.

Why would you like to avoid chemical stripper? The mess? the fumes?

Unfortunately it is probably the best option.

You ahould use an abrasive disc on a grinder to take 10mm back to bare metal all the way around the edges. Then use decent quality paint stripper to remove the rest. You can speed up the process with heat, more stripper, and covering the stripper in glad wrap while it reacts.

Only becuase of what I have read with a few issue where it can seep between panels and cause grief after painting. The other reason was if I was to do a panel with some surface rust, would this still work, or do you need to use paint stripper THEN remove the rust with something else? Abrasives seem to take care of both.

[timbosaurus]

Good idea!

I started by doing a quick sand, fill, spray in acrylic on my first car (KA laser). Well, it also had been in a rear-ender so needed a cut-and-shut, but my dad did that for me cos I was about 15 I learnt a lot about what not to do, but didn't really care, as it was a $200 car

The next one was a bare metal job on an absolute rust bucket celica. Cutting all rust out, using the mig to weld in panels, beating to the best of my abilty at the time and filling any remaining imperfections. I did this in acrylic as well for the good reasons Ian and TC1600 pointed out above. It's easy, forgiving, and simple to fix/patch up later.

<<<< and that's it there.

The most adventurous type of build is using the oxy for welding, file finishing the panels, and spraying in two pack. I am doing a good course at the moment for the finishing, but I will have to just experiment with the 2 pack painting. If you are fastidious and patient as you mention, the results and satisfaction of DIY bodywork are fantastic. I highly recommend it!

About the stripper, meh, don't stress. You would only really use it on the outer panels which don't really have many seams for it to sit anyway. The stuff is neutralised and washes off with water too.

If you want to strip the inner panels to bare metal as well (like the underneath of your boot), paint stripper would be a fkn painful process! Fortunately taking the interior back to metal is not necessary unless you are doing a concourse job, in which case you will probably dip/blast the whole job anyways!

Rust: People have different definitions of what surface rust really is, so you'd have to elaborate a bit. The definition of surface rust is the little bit of oxidation you get when bare metal is exposed to air for a few days. Any pitting or roughness of the surface is beyond "surface rust" and bubbles under paint are CERTAINLY NOT surface rust. But believe me, some ppl try to convince you otherwise when they are selling you a car

So saying that, if there is paint on the metal, there shouldn't actually be any surface rust. Maybe where there are stone chips, but thats about it. These can be touched up with some wet and dry and de-oxidised (rust converter is OK, but will eventually turn the metal black).

[twentyEight]

Sigmeister, there is some great info here to follow, and you've have made a great decision to research and practice before jumping head first into it...

The main thing I will recommend here is get yourself 2 guns... One for primer, and one for colour and clear...

Also, if you budget can afford it, get yourself a Iwata W-400 or LPH-400 HVLP gun for the colour and clear... They are extremely user firendly, produce a perfect spray pattern, and will last a lifetime... This is what I used professionally, and will purchase again when it comes time to spray my 28...

[Sigmeister]

The main thing I will recommend here is get yourself 2 guns... One for primer, and one for colour and clear...

Also, if you budget can afford it, get yourself a Iwata W-400 or LPH-400 HVLP gun for the colour and clear... They are extremely user firendly, produce a perfect spray pattern, and will last a lifetime... This is what I used professionally, and will purchase again when it comes time to spray my 28...

Thanks for the tip. I believe the gun I looked at origioanlly was like that. I couldn't be sure though. Actually.....I have a card with the part number. It's GNSU4000-20G and idea if that's the same brand?

My budget for the Spray gun was around $250.

So what's the main reason for 2 guns rather than 2 nozzles? It is just difficult to clean and swap them often?

I was thinking of getting a 2mm nozzle gun initally for the high build primer. Good idea?

[twentyEight]

Doesn't sound like the same brand, and an Iwata W-400 will probably set you back more about $350...

The 2 gun thing is a personal preference, as you have to pull apart the gun to clean it properly when switching from primer to colour and clear...

Paint and primer find the most difficult to clean spots to hide in your gun, and you shouldn't leave a gun soaking in thinners overnight or anything as the thinners will eat the seals...

One drop of colour in your clear (and vice-versa) will not harm the clarity or colour, but one drop of primer in your colour will effect the colour, and one drop of primer in your clear will effect the clarity of the clear!

I used a cheap gun for primer ($80 gun) and the Iwata for the things that really needed it...

[timbosaurus]

I used a cheap gun for primer ($80 gun) and the Iwata for the things that really needed it...

Very good idea!

I did the same thing. Used a cheapo Iwata ripoff (apart from the brand on the handle, could hardly tell the difference!) for the primer, and used dads old genuine iwata for the top coat.

I actually found the new ripoff better than the old iwata... probably just because the iwata was getting quite long in the tooth and probably needed a rebuild. That said, it did convince me that the cheap copies aren't too bad for the price, at least when they are new anyways.

[Sigmeister]

Thanks for the tip guys. If that's the case. I'll grab a cheapee gun (I assume it still needs to be a gravity fed HVLP) this weekend and give it a bit of a run providing I can get the boot in shape.

Oh, if I want to do the whole bootlid (Top and botton) what do you recommend for stripping the underside?

[o_man_ra23]

2 guns is the go. You can buy iso-free 2pak, and if your not painting metallic, these are fine without clear. For a metallic finish I would personally go a clear over base 2pak system. The base is a single part and hasnt got isocyanate. The clear can be bought as an isocyanate free product... not sure the brand, ask for it at your local paint shops.

As a tip from experience, dont sand your colour before putting the clear on... it just doesnt work Get a primer that is a similar colour to your finish colour. You seem to be doing blue, so get a blue or light grey primer. Primers that I know of are available as Red, Blue, Yellow, Grey or White, and there is light and dark in the Grey. There could be more, and many good paint shops can tint your primer (much better coverage on your base)

When you finish sanding your primer, if you rub through it at all, spray another light coat of primer over and give it a very fine sand to stop any circles appearing in your finish. (this applies to both 2pak and acrylic)

Use a very fine coat of black guide coat paint between sanding layers of primer to show up high and low spots. Also use a very long sanding block... As shown in this link to get good curves, very important when doing a Celica. This will provide an excellent flat finish, and worked extremely well for me when sanding an XA hardtop (large curved panels, came out fantastic)

When sanding between primer and base, its important to get all scratchmarks out... so put a very thinned out layer of primer on when you have finished filling, and sand with 1200grade wet/dry. If you are sanding between layers of colour, use 1500grade or lighter.

Preperation is everything, and if your not in a rush (ie, you dont need that panel for the car to function correctly) then being fastideous and picky is a good thing. Also after sanding and before re-coating, always use a soft clean cotton rag damp with wax&grease remover to remove any finger marks (body oils), sanding dust etc.

Dont wet rub bog or primer... they are porous and will fuk with your paintwork. Make sure if you do that you dry it thoroughly before continuing.

Leave the panel about 3 weeks between spraying the final coat of primer and your final sanding. Primer does funny things and can warp itself when drying, which will make your finish look wierd.

Hope thats not info overload, just trying to pass on as much knowledge as I can, as I learned a lot of these things either the hard way, or by listening to old panelbeater/spraypainters.