Carbon Guide Coat & Clear Coat

Chad.S

Chad.S

Oldtimer
There is a shop in Florida, that I have talked to a few times and follow their progress on IG and FB and I noticed on one of their posts that they use carbon guide coat between stages of sanding when wet sanding their clear coat. So I questioned this, he states that it really works to make sure that you are removing all of the scratches between grits..

Sure It would take longer because you put the carbon guide coat on dry but something I really struggle with is making sure I get all of the sand scratches out from the previous grits. Especially when I do many stages of sanding.. Such as when I block with 400 grit all the way up to 2000 grit, when blocking a whole car like this by yourself it can be very easy to miss a step.

I'm going to give this a try on my next big wet sanding project but it's going to be a while, has anybody else in here tried this process?
 
Is it carbon or is it 3m black guidecoat? If it is carbon what is the source? thx.
 
There is a local shop who does his clear wet sanding this way and swears by it. He sprays an over reduced base coat in a contrasting color between grits, I am not certain what a carbon guide coat is, maybe the substance used as guide is not important as long as it doesn't cause more work. His work is excellent and he does it this way with single stage as well. Key benefits to this is that he can answer the phone or work on something else and know right where he left off in the sanding process.
 
The carbon guide coat is just 3m's guide coat, it's applied with a foam applicator type pad.

I gave up on this style guide coat years ago because I liked the way the sem spray guide coat works and anything 3m is quite costly but for this application I am going to order some up and give it a try.. The downside is that I'm a ways off from paint on all of my resto projects, and I am not going to do this on a production type job.
 
does the dry guide coat work well with wet sanding? I would think it would wash off with water?
 
The dry guidecoat will stick good after the first sanding, seems to me I tried this years ago and decided it wasn't a good idea, I think I remember some of the powder acting like like loose abrasive but maybe it was my technique. Chad let us know how it works for you.
 
That dry guide coat can wash out of scratches a bit, so it's good to sand a little past the point where scratches aren't perceptible. Just have to remember it's a "guide," not a "bible."
 
I do mostly dry sanding now with eagle abrasives (thanks to JimC) so I like to use some water based pigment dyes as a guide coat. I use white over dark colors and blue over lighter colors. Since they aren't a hot solvent based liquid there's no chance of it staining or clouding up fresh clearcoat. Even if you want to wet sand with them the water doesn't seem to wash the pigment out of the scratches until they are gone. I use the colortone pigments from Stewart Macdonald, a guitar builder supply company.
 
this is one of the reasons i do one panel at a time. it is easier for me to keep track of what i am doing.
 
carson5150;35030 said:
I do mostly dry sanding now with eagle abrasives (thanks to JimC) so I like to use some water based pigment dyes as a guide coat. I use white over dark colors and blue over lighter colors. Since they aren't a hot solvent based liquid there's no chance of it staining or clouding up fresh clearcoat. Even if you want to wet sand with them the water doesn't seem to wash the pigment out of the scratches until they are gone. I use the colortone pigments from Stewart Macdonald, a guitar builder supply company.
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Nice tip! is this the stuff: http://www.stewmac.com/shop/Finishing_supplies/Colors,_tints,_and_stains/ColorTone_Liquid_Pigment_for_Waterbase_Lacquer.html
I might give it a try, mix with water and spray on or apply how?
 
shine;35032 said:
this is one of the reasons i do one panel at a time. it is easier for me to keep track of what i am doing.
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I have thought about it but I get worried my arm will get tired by the last panel and I won't sand it as well as the first.. lol..

In all honesty I may give this a try to.. I can clean each panel after I finish instead of the mess I tend to leave myself after sanding a whole car
 
when i stop for the day i know where i'm at. when i start the next morning i simply start a new panel. when i start buffing i dont find any of those spots i missed.
 
Sometimes I do the initial cut and just leave everything set and breathe for awhile, then go back and finish each panel one by one. That waterbased pigment idea for a guide looks like a winner for some of the steps, anything to eliminate under and over sanding to speed up the process.
 
It seems that years ago I tried the 3m guide coat for this and just made a mess an more scratches like bob said. But I decided to give it another whirl. Boy it is the complete opposite.

When I sit down and start a cut/buff job, I don't have the luxury of staying on it till it is done. I am in and out of the buffing room, constantly starting and stopping from dealing with customers and what not. This helps that since I can get pulled off right in the middle of doing a fender or a hood. I do the initial cut with 800 wet hard block. Guide coat, then 1000, guide coat again, then 1200. I'll go over it without any guide coat with 1500 and 2000 then 3000 and 5000. After the 1200 sand you have removed all of the coarse 800 and 1000 grit scratches. So I don't see much of a reason to keep using the guide coat. Those seem to be the ones that get you when you start buffing. What a difference it made. Reason I never though about using anything like that was the bad experience I got when I tried it last. I can't speak for any of the other powder guide coats. Only one I use is 3m.

What helps me also is doing a panel or 2 at a time and finish them all the way out and go ahead and buff them. Just breaks up the time some so you don't get tired of sanding/buffing as much in one session.
 
JeremyB,

I would like to get more details about your process using the 3M guide coat. You start with your initial cut with 800 wet. Then guide coat. Are you dry sanding at this point? Seems to me that the 3M powder would just wash off if using wet?

My biggest issue with the color sanding process, is in the sanding NOT buffing. I originally was skipping grits which Shine help me out on. It sure would be nice to now for certain that all the previous grit scratches are removed before stepping up grits.
 
Lighting plays a big part in seeing what you've done and are doing.
A halogen lamp can really show missed scratches when lighted at the right angle.
 
jeremyb;35377 said:
It seems that years ago I tried the 3m guide coat for this and just made a mess an more scratches like bob said. But I decided to give it another whirl. Boy it is the complete opposite.

When I sit down and start a cut/buff job, I don't have the luxury of staying on it till it is done. I am in and out of the buffing room, constantly starting and stopping from dealing with customers and what not. This helps that since I can get pulled off right in the middle of doing a fender or a hood. I do the initial cut with 800 wet hard block. Guide coat, then 1000, guide coat again, then 1200. I'll go over it without any guide coat with 1500 and 2000 then 3000 and 5000. After the 1200 sand you have removed all of the coarse 800 and 1000 grit scratches. So I don't see much of a reason to keep using the guide coat. Those seem to be the ones that get you when you start buffing. What a difference it made. Reason I never though about using anything like that was the bad experience I got when I tried it last. I can't speak for any of the other powder guide coats. Only one I use is 3m.

What helps me also is doing a panel or 2 at a time and finish them all the way out and go ahead and buff them. Just breaks up the time some so you don't get tired of sanding/buffing as much in one session.
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Well dang it I'm going to have to try it again then, unfortunately the next complete I have to shoot is a dark color.
 
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