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Matching Tricoat Pearls: Think Groundcoat

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Making a let-down panel doesn’t solve the problem of matching tricoat pearl color. There’s got to be a better way – and there is: an invisible foundation-coat repair.

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If an automotive painter were asked what he did for a living, it would be fair for him to say that he’s a master illusionist.

Citizen Jane bangs up her new white pearl Lexus and wants the shop to have it perfectly repaired before her husband gets back from his business trip. She is SURE that it won’t take long because it’s only a little scratch in the quarter panel, and she knows that it only took her two days to paint her entire living room. So how long can a little scratch take?

Meanwhile, back at the shop, Tommy Twotone, the head painter, is sure he just saw the boss estimating another one of those high-falutin’ imports with the pearl paint. Every time Tommy sees one of those hit the door, he dreads the days to come. Sure, the paint company rep said all he had to do was make a let-down panel (spray a little base, several 2-inch-wide strips, adding a coat of pearl every time, leaving him with a panel that he could take out to the vehicle in question and instantly see just how many coats of pearl it was gonna take to match that bad boy). Those paint guys have a way of making things sound SO easy!

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Just buy a few more cans of good old whatever it is and everything will be just fine.
Trouble is, more often than not, the let-down panel doesn’t match anything on the car. Too dark on the side, not bright enough on the roof, too much pearl effect against the deck lid. Tommy knew there had to be more to the problem than meets the eye. If only there were an Automotive Painting Channel on cable. After all, he learned a lot about cooking on that food channel …

According to reports from the vehicle model year 2004, white tricoat pearl paint was the second most popular color — with 17% of luxury vehicles sold in the American market being white tricoat pearl and a whopping 20% in the SUV/truck/van category being white tricoat pearl.

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These are significant numbers of potential customers for your shop. And these numbers are for the color white only. Many other tricoat colors are being used today — some of them contain pearlescent pigments and some of them don’t. Some are a modern variation of the old candy apple paint — a groundcoat, a tinted midcoat and clear to top it all off.
The overall effect of these modern tricoats is very pleasing to the eye. When they’re in need of repair, however, the level of difficulty they present requires an understanding of the paints themselves and of an effective refinishing technique (besides making a let-down panel). Without this understanding, you’ll feel very much like Tommy Twotone — dreading each and every time one of these vehicles enters your shop.

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About the Products
Titanium dioxide-coated transparent mica flakes are the original and still most widely used pearl additive. They reflect light and allow light to pass through them. The use of iron oxide and special pigments can create a metallic look.

But advances in pigment manufacturing have broadened the available palette of pigments. Those color-shifting hues we’ve all seen, starting with the Saleen Mustang, are the latest advance in multi-quadrant color technology. And there’s a new Borosilicate-based pigment platelet that developers promise will have more color purity and brightness than today’s pearls.

All of the pearl pigments we see used in automotive refinishing are used in a two- or three-stage painting system. A number of two-stage colors have varying amounts of pearl pigment in the formula, and the three-stage systems use pearls in the middle coats over a ground, or basecoat.

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Our concern today is with the three-stage systems.

I dug up a few paint formulas for the middle coat of a three-stage paint color — a GM white, a Ford metallic red and a Ford non-metallic red. Each formula is for mixing a quart of the needed color. Out of about 1,000 parts each, there are 56.8 parts of white, 40.4 parts of red and 32.9 parts of color. This is about 3-5% total color load in these middle coats. And it’s not unusual for the groundcoat to have more than 90% color load. Also keep in mind that these values are before reduction and application. (You can see a quarter in the bottom of a gallon can of ready-to-spray white pearl.)

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Now think about that let-down panel. One to two coats of ground, and generally one to five coats of the middle color. Says a technical manager at one of the paint manufacturers: “The let-down panel will help you match the pearl intensity, not necessarily the color.”

That’s because the relative strength of the middle coat in a tricoat has less effect on the overall color match than the groundcoat. If your groundcoat isn’t on the money, you will never match the vehicle.

You can keep painting, but there’s a better approach: Learn how to make an invisible foundation-coat repair. (You might have to check with your particular paint vendor to see which combination of products in their line will allow you to duplicate the method we’re presenting here.)

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We’re going to look at three possible repair/refinish scenarios, discuss effective techniques to deal with each of those scenarios and look at how you might possibly write up the final repair orders for each scenario.


Repair Inside a Panel, Only One Panel Affected
Our Caddy has a small dent in the front of the fender, just above the wheelwell. Our goal is to do an invisible repair and not involve the hood or the door and quarter panel. This example has a sharp upper fender line that allows us to backtape the top of the fender. A is the repaired spot. The areas A and B will need to be thoroughly sanded prior to painting.

Depending on your paint company recommendations, areas C and D will need to be scuffed and prepared to accept clearcoats. Because of the primer/surfacer, we need to use full-strength ready-to-spray groundcoat to achieve hiding in area A. When the primer is covered, cut the strength of your foundation color in half by adding a blending solvent or blending additive, and spray 1-2 thin coats, extending out past the repair into area C. Allow appropriate flash times. Generally, you’ll apply three to four coats of your pearl, or midcoat.

Start in the A-B area and extend the last coats out to the D area. Remember, these middle coats, by their very nature and design, are extremely transparent. After flash time, apply the appropriate clearcoat over the entire panel.

Repaired Front of Quarter, Blend and Clear Door
This second scenario (shown above) has a repair in the quarter panel that will require primer right up to the door, so the expeditious setup is to mask and prepare the door for a blend from the quarter and clear on the whole door panel. This is because virtually no vehicle manufacturer recognizes a solvent blend as an effective repair.


To achieve an invisible repair in this case, treat the areas A and B on the door like you would next to a repair, and prepare the remainder of the door per your paint company recommendations for blend and clearcoat. A will have some of the full-strength groundcoat, B to C will get the half-strength treatment to spread out the illusion you’re creating, with pearl coats fading out to the D area. You’re ready to clear the quarter and door.

Replace Door Skin/Shell, Blend Fender and Quarter

The last repair is door replacement on a tricoat vehicle. This leaves little choice but to extend your paint work fore and aft, including the fender and the quarter panel. You should have the adjacent panels prepped for paint and clearing but start out with the groundcoat on the door. Get a coat or two on that main panel before you pull the masking paper and extend your paint work into the adjacent panels. You already know what the A, B, C and D mean. Finish by clearing the entire side.


What Did We Learn Here?
I hope that you see the importance of focusing on the groundcoat. Learning to manipulate this part of the tricoat process will do more for your pearl painting skills than focusing on the pearl, or midcoat.

The photos are for the purpose of illustrating the method. Certainly, if the quarter goes into the roof and over to the other quarter, that’s an issue you need to address.
Keep in mind that paint companies and vehicle manufacturers recommend that moldings and weatherstrips be removed or isolated from the paint process. And if your repairs involve used panels, stripping of old finishes may be required and repairs in addition to paint times may be required.

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You’d be accurate if you concluded that I don’t place a lot of value on let-down panels. Too many supposedly “in the know” have placed far too much value for far too long a time on these. As mentioned earlier, a let-down panel will only help with the intensity of the pearl — it’s not going to magically lead you to a perfect match.

I believe that if you spend some time learning how to manipulate the groundcoat, learn to think “invisible” and practice the techniques described here, you won’t dread the next tricoat coming through the door. More importantly, you won’t waste valuable shop time repairing it.

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BodyShop Business contributing editor Michael Regan worked on the paint side of the collision repair industry for 36 years and lives in Northeast Ohio. These days, he can be found teaching cooking classes, playing guitar and piano and baking some of the best cakes that money can buy. You can contact him at [email protected]

Special thanks to Alan Craighead, technical manager at Sikkens Car Refinishes in Atlanta; Tom Bogo, owner of Lakeland Collision in Wickliffe, Ohio; the 3M Company, tapes/papers/DART tape; and The J.J.R. Company in Cleveland, Ohio.

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