How many strokes till the next grit?

F

Frank

I'm almost afraid to ask this question, but I gotta know the answer or at least something close. When wetsanding a panel, how does one know when to go to the next grit of paper. Usually I start with 1000 and sand till the op is gone. Then 1500,2000,2500,3000. Call me crazy but I gotta do it. Here's the issue...I don't know when to stop. Is there some sort of rule of thumb on this..say 50 strokes is enough to get you to the next level? I always feel like I'm going too far and cutting too much and end up into the basecoat. I sand too much with each grit I think, and in the process I'm taking more off than I should be. I'm sure all you guys have your own way of doing it, and I'm sure there's no real textbook answer here, But I sure could use a few suggestions on how I might do this better. As always I appreciate any and all input. Thanks Frank
 
Do you use a block? I usually use a block on the aggressive grits then switch to a soft pad with the finer grits. You can use the heavier grits to cut 75% of the peel out so there's only a speckle of minor shiny spots then switch over to the next finer grit untill the shiny spots are gone, then the next finer grit to remove the previous grit scratches. If your body work is straight use a block. Some of the blocks I use are made out of plexiglass in various sizes and shapes-if your block is true you can cut the distortions out with finer grits. Anyway you look at it if you're after perfection there is a whole lotta work-no using a DA for the perfectly straight stuff.
 
Guidecoating between grits is also an option but I had it bite me in the ass once and haven't tried it since.
 
Bob; I guide coat everything (using dry & wet guide coat) from filler, primer & even clear;

Just curious, why did it bite you in the ass?
 
Really I only do it when I want things really straight.

On my last project (which was white); I started with 600 wet; used spray guide coat; (makes it easy on my eyes; & I don't have to constantly dry to see where I am)

After that I used dry guide coat; which filled in all my scratches from 600 scratches; re blocked with 1000; dry coated again; used 1500 trizact; guide coated that it finished with 3000.

By doing that I knew I had all my prior scratches gone.

Worked like a charm. Same goes with silver. Have not tried with darker colors; because yet have had the oppurtunity. Shine might have mentioned baby powder?
 
Funny you mention Silver....This 86 Monte is Silver and black that I'm working on. Care to elaborate on this guide coat a little further? Did you just use cheap black lacquer for the GC? I'd like to try your method and see what happens. I've messed up every other thing on this job, heck one more screw-up can't hurt. Thanks
 
Frank,
Once you get the panel flat with your lower grits the process changes to removing scratches. As you move to the next higher grit you must be certain that all of the previous scratches are removed. One way to do this is on your final sanding say with 1000 grit be sure to sand in one direction let's say vertically. So all the 1000 grit scratches are now running in one direction. When you go to 1500 you want to sand all of the 1000 grit scratches out so you continue sanding (I sand in a circular motion) until there are no more vertical scratches showing (even faintly) on the panel. Then you should do your final 1500 passes say in a horizontal direction so that when you are done there are only 1500 grit scratches and NO 1000 grit. This is so important because when you move to 2000 grit it will NOT remove the 1000 scratches you missed.
When you get to 2000 the panel begins to shine again so your goal is to remove all remaining scratches leaving a consistent sheen to the panel. I do this by looking across the panel with some light shining on it. Halogen lights work well if you don't have windows or outside light shining in. As for a particular number of strokes per grit I do not think anyone can give that answer because there are too many variables.

Note: after I get the panel flat with a hard block I switch to a soft block/pad and I am not afraid to apply some pressure while wet sanding. You don't want to flex the panel but you can get aggressive with the finer grits as they are removing a minimal amount of material.
 
bubjel;1217 said:
Really I only do it when I want things really straight.

On my last project (which was white); I started with 600 wet; used spray guide coat; (makes it easy on my eyes; & I don't have to constantly dry to see where I am)

After that I used dry guide coat; which filled in all my scratches from 600 scratches; re blocked with 1000; dry coated again; used 1500 trizact; guide coated that it finished with 3000.

By doing that I knew I had all my prior scratches gone.

Worked like a charm. Same goes with silver. Have not tried with darker colors; because yet have had the oppurtunity. Shine might have mentioned baby powder?
Click to expand...

If my memory corrects me, Shine uses white pounce powder for guide coat on dark colors.
 
bubjel;1205 said:
Bob; I guide coat everything (using dry & wet guide coat) from filler, primer & even clear;

Just curious, why did it bite you in the ass?
Click to expand...

The clear must have been fairly fresh, I remember the spray on guidecoat or lacquer I used bit into the clear and I had a bad time sanding it off-I rmember telling myself not to ever try that again... I wouldn't try the dry guidecoat just because I've seen some larger chunks of carbon come out that would surely add some uneeded abrasive.
 
For anyone reading this that is new to colorsanding and buffing: if you plan to use a rigid block to do your colorsanding make sure your bodywork is straight or you'll cut through the clear on the high spots. Use a soft pad if your bodywork isn't straight.
 
Bob Hollinshead;1281 said:
For anyone reading this that is new to colorsanding and buffing: if you plan to use a rigid block to do your colorsanding make sure your bodywork is straight or you'll cut through the clear on the high spots. Use a soft pad if your bodywork isn't straight.
Click to expand...

Excellent point Bob.
 
That IMO would be considered a hard block as it's designed to hold it's shape and cut flat, I use some plexiglass and also aluminum blocks that really hold their shape. Soft blocks/pads-think foam, rubber, or a sponge that you can bend and will flex to adapt and follow different contours.
 
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