The Spray Painting Thread

[Lambolica]

It's official.... I suck at paint prep and application.

So Fucking disapointed at the results.

["Z" UTE]

Referece using prepwash/prepsol. The rag should never ever touch the lip of the prepswash container, do it once and ANY slight contaminant on the cloth will be present in every future application. Pour the prepwash onto the cloth. Prepwash has to be applied and immediately wiped off without the prepwash having a chance to evaporate, this means you have a rag in each hand, prepwash on and straight off.

Lambolica, add more thinners, and adjust your fluid flow to give more flow. 45psi is about right, but how long is your hose? Longer hose will give a greater pressure drop. Each of my hoses is about 7 metres, if I connect the 2 together I up the pressure by 5-10psi.

Overlap must be 50% to ensure an even coverage, anything else and you will get striping. The paint needs to be the consistency midway between water and mums dishwashing liquid. Heavy coats are a slower application of the same thinned paint, not a thicker paint batch. Your final coats can be as thin as water, just be careful not to apply too slowly to avoid the runs. My final coat of acrylic clear is normally about 10% clear and 90% thinners, it really brings up the gloss level.

EDIT 1.2mm or 1.4mm tip for top coats 1.8mm is way too big.

cheers Chuck.

[Lambolica]

Hmmm possible then that there was prepwash residue there still.

The final coats of clear were 30-70 and the speed of the gun slowed... = Runs

OK here is the wrap up.... I am trying to work out where I went wrong. Gun adjustment is where I'm leaning towards as the paint just seemed to spatter onto the panel, this is after several cleans.

The whole project went like this.

1. Stripped back bonnet using abrasive disc to bare metal (removed previous bog) Rubbed back with 150 sand paper.

2. etch primed the whole bonnet (using old shipon gun) application was fine.

3. Bogged up the areas that needed doing. and sanded back

4. applied primer over bog, and sanded back some areas, and reapplied primer, All sanding 150grit. This was 2 weekends ago

5. applied High fill primer, 2 light coats. had bad fisheye at first application. second went on fine. Friday afternoon

6. Sanded back using 150 then 400

7. another 2 coats of high fill. with new gun, fisheye, orange peel city. sanded back using 400 to get it smooth Yesterday

8. dust coat of primer and sanded back using 400. Was really happy with the prepared surface.

9 After washing with prewash, and wiping off with dry cloth (yes the prep was poured not held over the container) Prepwased before every application of paint. I shot a light coat of colour, which went on very dotted, second coat heavier (ie slower movement same mix), fisheyes/orangepeel/lifting. 2 dust coats in different directions. On closer inspection the primer was still showing through. 2/3 more thicker dust coats were applied. After the second coat I had the metallic streaking, this dissapated after the dust coats. There was about 10-15 min between coats.

10. Clear first coat was 66% 33% mix light dusting. second more heavy coat thinned down more (started to smooth the orange peel / fisheye) 3rd and 4th coats were thinner again, the 4th coat started running.

Photographic results :

Orange peel after second Coat, shot gives an idea of how rough



The following 2 shots are the crows feet and lifting that started after the first coat.





Finished bonnet after clear


You can see the lifting that seemed to continue (and is probably still happening)






It appears that I can see the outlines of wherever the is bog under the surface and this is where the lifting is starting, though there are other areas that are lifting also.




I'm trying to find a silver lining here but there is nothing good about the job at all. Annoyingly enough, the underside where I sprayed primer and 2 coat of colour only shows none of the defects. 3 weekends work down the toilet.

Tell me what has gone wrong here,

Cheers
Simon

[twentyEight]

The crows feet is where the paint is "frying"...

It is a chemical reaction with something underneath, most likely the primer.

Is it a 2k primer?

[love ke70]

stiggz had this issue when he sprayed his bonnet, same thing, everything was turning to shit around the bog areas, i think he put it down to paint stripper or something left behind underneath everything, but as you sanded everything to bare metal, thats not the case here.

what bog was it you used?

have you used it before?

very strange its all occuring at the bog areas , maybe list all the products you used, must be something not liking something else or there is something left on the surface, or which has soaked into the bog and is making its way out?

[Lambolica]

Nah It's all Acrylic based. I'll put a list together.

["Z" UTE]

Man that has turned out pear shaped. You will have to go back to bare metal and start again. Just a tip you could use here, everthing has to be spotless, I use sugar soap in hot water, for washing everything that has to be painted. I rarely use prepwash, because of the potential contaminent problem. For wet sanding I use the sugar soap and water as well.

After buzzing back to bare metal, coat with an epoxy sealer, these have etch properties, and are not as porous as primer. Re-bog, and hifill, and go from there.

Looking at the pics, there is way too much paint, and there is insufficient flash time. Thoroughly clean every orifice in the gun, including the air inlet at the top of the pot, you will have to strip clean the gun.


Bog sanding 80 dry -120 dry - 320 wet.

High fill sanding 320 -800 wet.

Denibbing 1500 wet.

Colour sanding 2000 wet.


The bog areas and edges can be a real problem if paint/primer is applied too wet.

Flash off time is critical, the paint surface will be dry to touch. If wet, allow more time to dry between coats

My suggestions are: High fill thinned 50% light coat, flash off then repeat till you get a film that is thick enough to sand flat. Laying on the high fill is not a great idea, as you will get lots of shrink back(crows feet). Sand wet with 320 wet then 800 wet. Apply colour within the hour of finishing your sanding. Single colour coat with 50% overlap, Allow max flash off time, and recoat. Repeat as necessary to get a good colour, but 2 coats should do it, three coats max. Allow max flash off then coat with 2 coats of clear allowing for good flash off between these coats. Avoid heavy single coats at all costs.

If you get a problem in the colour coat, stop and let the whole panel dry off, because you will have to repaint the entire panel, after you fix the problem area, as metallics do not respond well to spot repairs.

You will have to get the paint consistency exactly right. Metallics have to be mixed for at least 10 minutes to fully incorporate all the contituents of the paint. A broad paddle mixing stick lifting the paint from the bottom of the can is the way to go. Thinners have to be added to your mixing pot a little at a time and mixed in well before adding the next lot of thinners, otherwise you will have areas of shadow in the paint.
I use a 10 litre metal resealable paint can from a household paint supply shop as my mixing drum. 4 litres of paint and about 5 litres of thinners is the mix I aim for. After about 20-30 minutes of mixing, and it is fully mixed, I decant what I need (600ml for a bonnet) into a 4 litre can, and adjust the mixture by adding about another 5% thinners. Strain the paint through a cone filter into the gun pot and away I go.

Temperature and humidity play an important part in the application of all auto paint, do not paint when the humidity is above 60%. Air temp has to be 15 degrees as an absolute minimum.

Hope this helps, cheers Chuck.

["Z" UTE]

Oh yeah I forgot to mention, you will need a LONG sanding block to do those bog repairs. A small block will get you into a lot of trouble, as the small block will not sit on the panel like a long block will. Small block = low areas. Do not forget to use a guide coat when doing your final primer rub down.

cheers Chuck.

[pac]

wow what a mess you have gotten yourself into, you have two choices strip back to metal which now that i see the problem is what you should have done in first place, or to save your self heap of work rub down wet 240 and apply an isolator and then you will be able to paint again. But by your pics you are putting paint on way to thick, after all your preping any spray shop would have painted it for you for couple hundred

[Lambolica]

I appreciate your input Chuck. I have comments inline in red

I was never happy with the residue left by the wax and grease remover as I couldn't get it to come off. In future I would probably use water to wash the prewash off. I'll go with the sugar soap plan, as I was tempted to use a little washing detergent in the wet sand water.[/COLOR]

After buzzing back to bare metal, coat with an epoxy sealer, these have etch properties, and are not as porous as primer. Re-bog, and hifill, and go from there.

I used a Dulux product (the same that the panel beater is using on the GT)

Looking at the pics, there is way too much paint, and there is insufficient flash time. Thoroughly clean every orifice in the gun, including the air inlet at the top of the pot, you will have to strip clean the gun.

There probably is too much paint, however the paint was touch dry when the next application occured. Herein lies part of my problem. You mention below that you decanter 600ml to do a bonnet, is that per coat or for the total paint coverage?

I was using in the order of 500ml per coat and it just wasn't going onto the panel well. The best way I can describe it is it spattered the paint. My stroke on the dust coat was probably 3-4 seconds for the length of the bonnet which resulted in a sandpaperlike finish and after the second coat I could still see primer in the low areas of the fisheyes. The heavier coats were probably 6-7 seconds and was far too thick and the metallic started stripeing. I was holding the gun about 10 inches from the panel spray pattern was 8 or thereabout inches wide 50% overlap. Gun was cleaned during each flash off period by way of pulling out the needle and cleaning, pulling the nozzle of and soaking in thinners and cleaning with a brush an pipe cleaner (came with the Gun).

I just couldn't find the balance of paint and air that would lay down a wet, even, relatively flat coat. The air comming out just seemed to create the orange peel effect and not self level like my previous attempts have done with the siphon gun

Bog sanding 80 dry -120 dry - 320 wet.

High fill sanding 320 -800 wet.

Denibbing 1500 wet.

Colour sanding 2000 wet.


The bog areas and edges can be a real problem if paint/primer is applied too wet.

Flash off time is critical, the paint surface will be dry to touch. If wet, allow more time to dry between coats

My suggestions are: High fill thinned 50% light coat, flash off then repeat till you get a film that is thick enough to sand flat. Laying on the high fill is not a great idea, as you will get lots of shrink back(crows feet). Sand wet with 320 wet then 800 wet. Apply colour within the hour of finishing your sanding. Single colour coat with 50% overlap, Allow max flash off time, and recoat. Repeat as necessary to get a good colour, but 2 coats should do it, three coats max. Allow max flash off then coat with 2 coats of clear allowing for good flash off between these coats. Avoid heavy single coats at all costs.

If you get a problem in the colour coat, stop and let the whole panel dry off, because you will have to repaint the entire panel, after you fix the problem area, as metallics do not respond well to spot repairs.

You will have to get the paint consistency exactly right. Metallics have to be mixed for at least 10 minutes to fully incorporate all the contituents of the paint. A broad paddle mixing stick lifting the paint from the bottom of the can is the way to go. Thinners have to be added to your mixing pot a little at a time and mixed in well before adding the next lot of thinners, otherwise you will have areas of shadow in the paint.
I use a 10 litre metal resealable paint can from a household paint supply shop as my mixing drum. 4 litres of paint and about 5 litres of thinners is the mix I aim for. After about 20-30 minutes of mixing, and it is fully mixed, I decant what I need (600ml for a bonnet) into a 4 litre can, and adjust the mixture by adding about another 5% thinners. Strain the paint through a cone filter into the gun pot and away I go.

Temperature and humidity play an important part in the application of all auto paint, do not paint when the humidity is above 60%. Air temp has to be 15 degrees as an absolute minimum.

Hope this helps, cheers Chuck.

Obviously the paint is too thick and the the gun not set up correctly however the crows feet are what annoys me, I do note however that the mirrors that had sweet FA prep came up as I expected (bar a few runs) the High fill primer wasn't used, nor was the prepwash (water only)

CHeers
Simon

[Lambolica]

Pac, the point of the exercise is to learn the art, to paint a whole car at some stage, I would have been a simple thing to take it out to the guys who are doing the GT and get them to do it.

I am leaning towards 2 issues here,

1. the paint to thick

2. either the prepwash residue or the High fill. All of the Bog / primer / High fill primer was septone stuff as was the prepwash

I have started sanding it down flat, and no surprises the crazed areas the blue high fill is showing thru.

On the paint gun side of things any tips on how to set it up to deliver the right consistancy of paint?

Cheers
Simon

[o_man_ra23]

do not paint when the humidity is above 60%.

I don't think humidity gets below 60% up here?? Man, I'm boned then!!

[o_man_ra23]

I think I mentioned it earlier in this thread Simon, but I had an issue where paint was going on too dry and splattering, going like sandpaper. Just as you describe. Turns out it was the air breather to the pot was clogged, causing a vacuum in the top of the pot, and thus the paint couldn't be sucked out of the bottom properly. Try cleaning that pissy little breather up the top of the pot and see if that helps. It completely changed the way my paint went on for that job (RA23, Protec acrylic in 352 Orange)

[Lambolica]

I didn't have the breather in there.

["Z" UTE]

Simon the Septone stuff is ok for small paint jobs. However there seems to be a problem with its ingredients when used on a large scale paint job. I had painted one of my RA28's with Septone, and had to take it back to bare metal and start again. I now only use PPG, or Glasurit paints. If a customer wants something painted with their own brand of paint, I get them to bring me the same brand of thinners, primer and hi-fill. I will never mix brands, not even thinners.

General purpose thinners is only good for mixing with primer or cleaning guns, nothing else.

Midway thinners is what I use on a daily basis for topcoat and clearcoat.

2 Pak thinners seems to work exceptionally well with clear acrylic, giving a nice flow levelling time without excessive tendancy to run.

Looking at your spraying techniques, the sand paper finish is caused by high air pressure.

The mottled clumping with no coverage or "flow" is due to the paint mix being too thick. The thinning guide on the paint manufactures can is only a guide, and does not take into account any open time, when the solvents have ben evaporating from the paint, nor does it account for solvents lost due to a bad sealing container. My acrylic mixture is never less than 50% thinners.

Does your gun have an air pressure adjuster at the base of the gun handle? If so open the air flow to max, with gun in hand go back to the compressor, and adjust the compressor outlet pressure to about 45psi. Spray a test piece, and adjust the air pressure at the gun down to suit a good spray pattern, or adjust up at the compressor. Better to be a little high at the compressor, as you can trim back at the gun.

Gun held steady about 200-250mm above the surface of your test piece spray a 0.5 second burst. Your pattern should resemble a cartoon type cigar, fat in the middle and thin at each end, and should be about 120mm long. Adjust your airflow at the gun head to get this pattern. If that test runs, trim back on the fluid feed. that about does it for gun set up.

Any of the paint ot bog that has been applied needs to be rubbed back to break the seal film on top of it. If you spray directly onto any unsanded area the paint will not bond, the only exception to this is if you coat straight after flash off. You must use a guide coat, to ensure you break the film in even the smallest of indentations.

When you have the bog back in, and sanded, you could try dry spraying around the edges of the bog, basically hold the gun 600mm+ off the job, and spray lots of light coats over a long period of time. If you get the primer wet and glossy at this stage you will get the dreaded bog halo effect again. Let the primer well and truly flash off, then prime the entire surface of the bonnet.

Stroke time, front to rear of a TA22 bonnet should be around the 5 second mark

Good luck with the next application, cheers Chuck.