Pigtails - Need help figuring out cause?

[Mike Phillips]

Just to add...


I don't do any dry sanding. I don't like the dust mess and I don't want to have to wear a respirator. Too much dust for my taste.


So knowing all my sanding is wet, be it by hand or be it by machine, I've NEVER seen this much pig tailing with my work. Never.

I do change out discs as needed. I try to squeeze as much use out of every disc I use simply because my parents taught me not to be wasteful. So I try to be a good steward with all of Autogeek's resources.

The last car I machine sanded was a 1970 340 Charger R/T with DIP or Dirt in Paint. I machine sanded twice, once with 3M Trizact #3000 followed by 3M Trizact #5000. Zero Pig Tails.



Machine sanded with 3M Trizact




Final results



And I would say after compounding out sanding marks, the paint was on the Medium/Hard side of the Paint Hardness Spectrum. Definitely not soft. Also just to note, this is a 20 year old basecoat/clearcoat paint job.




Assuming Matt is swapping out sanding discs and above all - working clean, that is clean car, clean shop, clean sanding lube, clean everything, it's my hunch the problem is the paint is too soft. This is why I suggested the shop call in the Paint Rep and have him do some investigating into the paint process.

Instead of trying to fix the problem at the sanding and polishing step - first investigate upstream and make sure there's not a problem in the painting step.


It's one thing if you're going to paint, sand and buff a care ONE TIME. It's another thing if it's a running business or a running process. The process needs to be looked at and if something is amiss then fix it where it's at, don't band-aide it downstream.


Again - I've never experienced pig tails that look like this.

[2black1s]

While this post doesn't directly address the "pigtails", here's some of my general thoughts on sanding and polishing fresh paint. Some of these same comments, I have expressed previously in other similar threads.

I understand the desire to sand and polish paint as early as possible after painting to help with productivity, but that has never been my recommended process.

Whenever I did my "top notch" paint jobs I would always wait at least 60 days before sanding and polishing. This gives the paint (and primer surfacers) the necessary time to fully "shrink-up" and harden before polishing and that results in a more permanent finish. Many times when a new paint job is sanded and polished within days of painting, the initial results can be stunning, but a few months down the road the paint's finish and gloss level will have diminished slightly. This is a natural phenomenon as the paint cures and is referenced in other threads as paint "hold-out" or paint "die-back".

All of my final sanding is done by hand. I would never use a DA (or any machine) for final sanding. I don't care how good you or anyone professes to be using a machine for final sanding, you will always have better control and precision by hand. And when you're doing the final sanding on a "perfect" paint job, isn't that what you're looking for - absolute precision?

And then, hard rubber blocks are another no-go as a primary tool for final sanding in my book. My final sanding is primarily done with a soft rubber or sponge pad that can follow the contours of the surface being sanded. This is because there are really no perfectly flat panels and even if there were, with the final sanding you are only trying to level the paint's texture, nothing more. All other straightening and flattening should have been done before the paint was ever applied.

Now I completely understand that every paint job is not the "perfect" paint job and as such compromises are made and accepted. Sanding and polishing "too early" is one of those compromises. I've certainly done it.

[Mike Phillips]

I was hoping you would see this thread and chime-in. I know I always appreciate your input.

I understand the desire to sand and polish paint as early as possible after painting to help with productivity, but that has never been my recommended process.

Just to add for everyone that will read this into the future.

There's a difference between the type of work done at a collision shop and a custom paint shop or restoration shop. At most collision shops, if they are a successful business, cars are coming in, getting fixed and then leaving. They are at the shop for days, not months. For custom work, there's more time allotted for the work and the car can remain at the shop for extended time - or be brought back.

I just want to share that there are reasons why some cars are painted, sanded and buffed in days or a week or two while others cars have the luxury of having more time for the work to be done.

Whenever I did my "top notch" paint jobs I would always wait at least 60 days before sanding and polishing. This gives the paint (and primer surfacers) the necessary time to fully "shrink-up" and harden before polishing and that results in a more permanent finish.

Many times when a new paint job is sanded and polished within days of painting, the initial results can be stunning, but a few months down the road the paint's finish and gloss level will have diminished slightly. This is a natural phenomenon as the paint cures and is referenced in other threads as paint "hold-out" or paint "die-back".

I'm so glad you shared the above. I completely agree with the above process. If a car can be left along for weeks or even months before sanding and buffing the end results will look better and look better longer due to the reasons 2black1s shared above.

I also want to share a WORD I learned from a painter friend of mine that is the word he uses to describe what happens to paint as it continues to dry and cure after painting.

Shift


Once when talking to him I asked him how long he likes to wait after spraying a car before he sands and buffs the paint and his answer was he likes to 3-4 weeks to give the paint time to SHIFT.

The word SHIFT in this context means not only to fully dry, cure and harden, but also time for any solvents to evaporate out-of and off-of the paint. It also means for the paint to MOVE or SHIFT until it's happy. And this means that as the paint is drying, it's going to shrink and shrink means MOVE or shift.

Body panels are also going to expand and contract as temperatures rise and fall and all these things, the curing, drying, expanding and contracting affects the paint in the first few weeks (or months), until the paint reaches a point where it's done shifting and it settles into it's permanent location and also permanent STATE of being.

Then it's time to sand and buff.


Love that word - shift.

And of course, depending upon the shop and the project - not everyone or every car has the luxury of just sitting around a body shop for weeks or months for the paint to shift before the technicians sand and buff and that's why for a lot of "Daily Drivers", any fresh paint work that is going to be sanded and buffed is often times sanded and buffed within days of popping out of the paint booth instead of months.

As a new wrecked car arrives at a collision shop - another must leave - most shops only have so much real-estate to park cars.



Thanks for chiming in 2black1s - I wish I could remember everyone's real name.


Mike

[Mike Phillips]

My final sanding is primarily done with a soft rubber or sponge pad that can follow the contours of the surface being sanded.

What do you think of these?




The above is a medium soft rubber hand backing pad from Meguiar's.


It fits a half sheet perfectly. I show it because we sell it but I've also been using it since going to work for Meguiar's back in 1987.


Have you ever used one of these?

[2black1s]

I was hoping you would see this thread and chime-in. I know I always appreciate your input.

...


Thanks for chiming in 2black1s - I wish I could remember everyone's real name.


Mike

Thanks Mike! John

What do you think of these?




The above is a medium soft rubber hand backing pad from Meguiar's.


It fits a half sheet perfectly. I show it because we sell it but I've also been using it since going to work for Meguiar's back in 1987.


Have you ever used one of these?

I don't recall ever using that exact pad. The ones I use, made by 3M, look nearly identical and from your description they sound very similar too.

[Mike Phillips]

Thanks Mike! John

I'll try to lock that into my knower. It's getting a tick full now days.

I don't recall ever using that exact pad.

The ones I use, made by 3M, look nearly identical and from your description they sound very similar too.

There is a similar flexible rubber block from 3M and also a thinner version with holes in it if I remember correctly.

PM me your shipping address and I'll send you one to inspect and test out. Then share your thoughts as I would respect your opinion.

[Cosmin]

with older, restore or repaint cars , sometimes i seen a lot of sanding marks , pigtails that were in the prime , or color , and clear coated after... but still visible , just a thought
* if that`s the case is not much to do.

but if on the clear than probably , like was mention before because is a soft paint , also the jump #500-#1000

[TMQ]

with older, restore or repaint cars , sometimes i seen a lot of sanding marks , pigtails that were in the prime , or color , and clear coated after... but still visible , just a thought
* if that`s the case is not much to do.

but if on the clear than probably , like was mention before because is a soft paint , also the jump #500-#1000

That's the conundrum...Is it in the clear? Base coat? or in primer?

One thing you can do---wet sand lightly on clear coat. Buff out and there's a bitty change, then you'll know it's in the clear coat and can be taken out.

Tom

[2black1s]

with older, restore or repaint cars , sometimes i seen a lot of sanding marks , pigtails that were in the prime , or color , and clear coated after... but still visible , just a thought
* if that`s the case is not much to do.

but if on the clear than probably , like was mention before because is a soft paint , also the jump #500-#1000

That's the conundrum...Is it in the clear? Base coat? or in primer?

One thing you can do---wet sand lightly on clear coat. Buff out and there's a bitty change, then you'll know it's in the clear coat and can be taken out.

Tom

Scratches buried beneath the clear in the color coat are usually pretty obvious to the trained eye and are a totally different type of defect than the one being discussed here.

The primary cause of such defects is from finishing with too course of a sanding prior to applying the primer surfacer and topcoats. In such cases the primer surfacer has to fill-in those sanding scratches. Most primer surfacers will easily fill-in sand scratches if you were to stop at that point. The problem occurs when the topcoat is applied.

The solvents in the topcoat will penetrate the primer surfacer and cause what is known as "sand scratch swelling" of the underlying scratches. You can sand the scratches out but as soon as you apply another coat of the topcoat they will re-appear.

Depending on the severity and the type of paint being applied these scratches may re-appear immediately following the topcoat application, or in less severe instances or with less aggressive paint types the scratches may not show up until the curing (and inherent shrinking) process progresses.

In the case of solid colors these scratches can usually, depending on severity, be sanded and polished out once the paint is fully cured.

That is not the case with metallics with their reflective characteristics. Even when you sand and polish the clear coat as perfectly smooth as possible, the metallic particles will transmit the scratch appearance through the clear coat because of their irregular orientation resulting from the underlying scratches. If this is what you are dealing with, there is no fix short of stripping and repainting.

[MattyJ]

Thanks Tom, the pigs are not the big deep ones from dirt but smaller and many.

As far as sanding I am responsible for all sanding and buffing. The painter just sprays his best and says here you go.