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      10-08-2020, 02:43 PM   #63
Private First Class

Drives: 14 335ix M Performance Edition
Join Date: Jul 2016
Location: Victoria

iTrader: (0)

01/10/20 Mirror housing replacement, part 1 of 3

Let the madness continue..

Picked up a set of aftermarket 6pc M4 mirror housings for the M2/F30 off of eBay from a vendor called bulbxpert. I'm sure most of you know which ones I'm talking about; however, if you don't, they look like this:

I will say right out of the box; for the price, the fit and finish was very good. That being said, I had two niggles with the mirrors that I had to address before installing on my car.
  1. The mirror caps were black which IMHO didn't suit the look of my car, and
  2. My car has top view cameras fitted in the factory mirrors, I wanted to maintain that.

The first item was relatively "easy" to deal with. I bought a pint of color matched B44 Valencia Orange automotive paint, a quart of 2K clear coat, a Pro-Tek 2500 mini HVLP gun and a bunch of various painting supplies (PPE, sandpaper, thinners, etc).

This should've been a straightforward job; rough the surface with a grey scotchbrite pad, wipe down, spray the color, spray the clear, let dry...

Well I can tell you this, spraying automotive paints out of a HVLP gun is a WHOLE different ball game than airbrushing models with acrylics.

Lesson #1, and #2: Acrylics dry from the substrate outwards, where solvent based automotive paints dry from the outside going towards the substrate. So acrylics can be laid on thick, solvent based paints cannot. Have you ever heard of a term called "solvent pop" before? Yeah me neither.

I didn't know that if you never allowed the base layer enough time to fully kick or you put the clear coat on too thick could cause this issue.. The result, you end up with a million tiny little bubbles just below the dried clear coat surface. Only way fix the problem is to remove the paint you just just applied. Needless to say those two lessons caused me to strip/reshoot the mirror caps twice.

Lesson #3: MAKE SURE that the bucket you're using to wet sand with is SPOTLESSLY clean. I.e., don't do that brake job on your car, use a bucket to wash the wheels and brakes, then later in the evening decide to finish-up wet-sanding the part you're planning on painting the next day using the same bucket as the brake job. If you do, get ready for your part to be covered in fish eyes. As you've already guessed, only way to fix the situation is to remove all the contaminated paint, re-sand the surface, then re-reshoot. So add another strip and respray.

Lesson #4: Mottling. Ever hear of that term before? Me neither, until now.
This is the bane of any painters existence when they're shooting metallics because you don't know you have a problem until it's too late to correct. If your gun pressure is off (too high or low), if your spray technique isn't perfect (too fast, too slow, not enough overlap, not at 90˚ to the panel), if the paint mix is off, or if your "drop coat" was too light.. all can cause this issue to crop up.

You might ask, "when will you know if you have a mottling issue?" You get to find out AFTER the clear has dried that you now have a tiger striped or darker non-metallic streaks in the base coat.

Then you might ask, "how do you fix the issue?".. well guess what, you now have to reshoot the base coat which requires removing the clear if you don't want your panel to be 10 inches thick.

Add another strip, and reshoot.

Lesson #5: Edge mapping.. If you're like me, and you had to apply paint five different times by now cause you kept screwing up, but you're too stubborn to stop trying.. you might've sanded into the substrate material in a couple spots. Well, I'm going to tell you a little secret; learn from my mistake and just remove all traces of paint and take the part back to bare plastic and/or metal and start from scratch. Save yourself the time and effort. Because if you don't, the thinners in the primer you just sprayed over the top of those bare spots could and probably will cause edge mapping to occur. Add another strip and respray to the list.

In case you've lost track of what painting attempt I was at, I'm now on my seventh attempt at spraying the mirror caps. This time, I started with bare plastic, sprayed some plastic bumper primer, sprayed the base coat, then sprayed the clear.

Did it turn out perfect? No. Is it good enough for an outdoor spray job on a daily driven vehicle? You betcha it is.

Primer on

Base & clear on

After a wet sand and polish to remove dust spots and a little orange peel in a few spots

Comparison to car in full daylight

You might ask, total cost for the respray to this point: $130 cad and ~15 hours worth of work fixing my mistakes. haha

Next up, camera mounting...

Last edited by zibbit; 10-08-2020 at 09:06 PM..