Dipping toe into painting

Has a spray window from 8 to 10, picking 9. Check list ready to go for the crucial final coat. I want no more mistakes, and am getting rather bored with the panel.

SUPPLIES AND MATERIALS
======================
Respirator, clean
Gloves
Paint
Strainer
Thinner
Waste thinner
Tin openner
Mixing cup
Stirrer
Pipettes/scoop
Paper towels
Airtight rubbish bag
Stand, wrap, and tape
600 grit sandpaper
Nozzle socket and wrench


BEFORE SPRAY
============
Tighten gun nozzle
Flush gun and line
Set gun controls
Set compressor pressure
Check needle sealed
Dust off panel with brush or spare gun
Strain paint
Test spray


BETWEEN COATS
=============
Seal gun tank vent
Stopwatch
Sand out debris, brush/wipe off dust, dry
Unseal gun tank vent


AFTER SPRAY
===========
Dispose paint
Seal tank vent
Fill tank with cleaner
Check needle leak
 
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I ended up with a peely finish today. 2 turns from closed at 1.5 bar didn't work, giving a dull and dry look. I tested by going over with more passes. That made no difference. 2.5 turns from closed was better. Testing has to continue before the right setting can be discovered. Previous accidental 2 bar full open did work but most of the paint was blown into the air. This made the setting not practical.

Other than the peel, there is no serious dirt issues that can't be sorted out with 1000 grit sanding. So, the panel will be finished after curing. The peel will be improved by hand polishing using cutting compound.

The colour match isn't perfect but passable. I will now commit to a full tin of paint for painting the actual panel I wanted to sort out.
 
The next panel is the side skirt. It is estimated at less than 320mm x 2000mm = 0.64m^2. This is around 6.25 times the size of the current panel. It looks very do-able for the compressor. The primer and base coat should be easy-piecey. This is a serious panel, and I will be using the R500 exclusively. The panel has been taken off the car to make the job easier.
 
Training panel complete and going on the car. It's peely left and right (relative to the image), less peely middle and bottom. The debris on the final coat was sanded out and polished, leaving no marks. Wet sanding was possible for the whole panel and could produce significantly better result. I will leave that for the next panel if there is a need. This is the first time I looked into wet sanding and it is easier than I thought. With enough meat on the tough 2k clear coat, risk of doing damage from sanding is low. I am now biased towards higher paint flow when clear coating, with exception of the first coat. A thinner first coat reduces the difficult in dealing with debris that might be in contact with the base coat.

A dirt spot that was repaired by breaking all the way down to the base coat, without touching the base coat, was invisible in the final result.

A dirt spot that was repaired by breaking all the way down to the base coat, with the base coat roughed up slightly, was visible in the final result.

traiuning-panel.png
 
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Priming for the 4th panel was completed using R500, 1.3tip, 1.5bar, 3flow, 150ml. The result was pro quality. I estimated the paint requirement at 90ml, but gave it 150ml to allow for transfer loss from containers, strainers, etc. In the end, 150 was a little more than the actual requirement, but not by too much. The same volume should be plenty for the base and clear coats.

There were no serious dirt and dust issues today. I had a large-ish piece of wood splinter going on the wet primer that I quickly picked off with a blade. A blade has to be added to the checklist of material requirements. The checklist was very effective in speeding up the process and preventing errors.

I will be filling imperfections in the panel by hand brushing additional primer and sanding flat. Hand brushing will enable a thicker fill. I will be sanding smooth the primer on the normally visible face of the panel using 600 grit. The panel was prepared using 400 grit before priming. A common suggestion was 320-400 grit.

Not having a gun stand was a significant annoyance. But, an improvisation using the corner of a box was found and acceptable. I could use a smaller cardboard box.

The compressor performed admirably, not a single moment of lost pressure. I counted to 10 between full length passes. 10 would be needed for 2 bars, less for 1.5 bars. Remembering a single number is the easiest.

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The primer was easy as I thought. Since I had no major fixes/fills to do, brushing on primer for minor fixes was OK, following by sanding flat. A second coat of primer was made after fixes. The optimal flow rate was found to be at 3.5 turns from closed. While laying down the primer, a ripple effect could be seen on it, indicating an apparent too much material. That was only temporary, it then flattened out while drying. This gave a smoother finish. Appearance of temporary ripples was indication of good flow setting. This speculation was applied for the base coat and it was effective.

Laying down the base coat was easy enough. But it was plagued by white specks of pollen. Unlike the primer, the final coat of the base could not be sanded or manipulated to remove debris without making a mess. This made it significantly more difficult than I hoped. This resulted in applying more and more layers of paint. New layers then attract more pollen. It's a bugger. I attempted spot repair using a 0.3mm tip air brush. It gave a much finer paint texture that reflected the light differently. That was a no go.

The optimal gun setting for the base was: R500, 1.3tip, 1.5bar, 2flow.
 
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The base coat was finished close to perfection. Spot repairs using the normal spraying gun settings was effective in blending in the new paint. Total paint used for the panel was about 250ml. The most effective way I found to remove debris on a coat was rubbing it out through a dragging motion using 600 grit under the thumb. This produced a small repair area. Wetting by washing up liquid and water helped it along.

It's becoming obvious 1k paints are quite good for DIY when the spraying conditions are not ideal. 1k paint dries fast and allows quick repairs within the same spraying session. But 1k paint hasn't the durability. I had 1k clear on the panel previously. I thought the clear had delaminated. It turned out patches of clear were completely gone. What remained, stuck on fine, and I struggled to sand them off. The base coat was also fine.

My next step is to do 2k clear. It's going to be a very slow process because debris fixes can't made until after a day worth of curing.

In terms of my painting skills, priming and base coating are in the bag, despite the challenging spraying environment.

I have one more buy to do with painting, a de-nibbing tool. This will remove debris on hardened paint. Probably won't work on softer new paint.

denibbing-tool.png
 
Finished the first clear coat this morning. To counter debris issues, the painting surface was arranged to be laying vertical like a wall picture. If anything got on it, there would be less chance of gravity pulling the debris down to contact the base coat. How well that worked wouldn't be known until cured.

Used R500, 1.3tip, 1.5bar, 2flow on the smoother surface (the normally viewable face) of the panel, where the primer was sanded flat. The finish was less peely, but the mirror effect was worse. There was a minor run.

Used R500, 1.3tip, 1.5bar, 1.75flow on the rougher surface (the bit that normally faced the ground) of the panel, where the primer was not sanded, and small stone impact damages were left unrepaired. The finish was more peely, but the mirror effect was better. It was newly understood orange peel came partly from non-flat primer, or base coat.

The optimal gun setting for the clear coat is estimated at 1.5flow, and that's what I will use for the second coat.
 
There is a lot more to painting than spraying. Colour matching is also a large part. I could potentially modify the final result by manipulating the primer colour. One possible approach is to get separate black and white primers. Then mix the two using various ratios until the right end result is produced.

 
To keep things simple and avoid flipping the panel about risking dropping it, I decided to paint the second coat on the side face of the panel only. The bottom face could wait. The knowledge for doing a mirror finish was gained over night from my experience of the first coat and re-watching painter videos to confirm my deductions. The secret recipe was found! For the outer coats of the clear, thin coats must be repeatedly laid to build a thicker coat. A thin coat can be achieved by higher pressure (what the pro's do), or lower material flow (what I do). Excessively low flow can result in a dry finish, so it has to be used with great care. High pressure results in material waste, misting the neighbourhood, and not my preference.

I used R500, 1.3tip, 1.5bar, 1.5flow, 45ml paint on the second coat. Painting the panel as a vertical surface did stop debris penetrating the wet clear to reach the base coat. This allowed me to sand out all of the pollen on the first coat without touching the base coat. Success in this inflated my ambition, which resulted in my finding more and more flaws to fix. Some of these flaws were on the base coat. Scuffing up the base coat ruined the final finish. So I have several small patches of light or dark depending on the viewing angle. I will leave these as reminders of what happens if you don't know when to stop. In conclusion, a tiny dot of dirt is preferable to a patch of scuffed up base coat.

After curing, I will have a flatter finish than what I have now. Wet sanding won't be necessary.
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I have decided to not give the bottom face a second clear coat. Nobody looks at the panel there apart from the MOT guy. Also, it doesn't suffer from UV there, hence no risk of paint failing. For the side face, since I have to sand out debris anyway, I might as well wet sand the whole face. It's not going to be hard to do. 1500 grit will be used with washing up liquid water, followed by hand polish with cutting compound. The panel has too much shine at the moment, and I wouldn't mind dulling it a bit.

I held the panel at the normal mounting position on the car for a quick check. From some angles, it looks like a match. From other angles, it looks light. The primer colour needs work. My next task will be to get a tin of black primer to mix with what I have, and experiment a little. Spraying a bunch of expired credit cards will give me something to place on the car to do colour comparison. Little jobs will need a little gun. The R100 fits right in.

This concludes my toe dip into painting, it was gainful. If there is another stretch of calm weather in autum, and the right primer colour has been worked out, I might paint the same panel on the other side of the car. Perhaps, there will be less of a pollen problem then? Open air DIY painting not only depends on the direction of wind, it also depends on the season. Open air has its advantages. Paint solvents are nasty stuff. Paint thinner fumes alone can dissolve paint and some plastics. You don't want it in enclosed spaces, unless you have pro venting.
 
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DiyNutJob said:
. For the side face, since I have to sand out debris anyway, I might as well wet sand the whole face. It's not going to be hard to do. 1500 grit will be used with washing up liquid water, followed by hand polish with cutting compound.
Click to expand...
Oh dear
 
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