Truing the block when wetsanding.

Concours.John

Concours.John

Auto Detail & Restoration
There has been talk about wetsanding this is more focused on hard blocking. Most if not all hard blocks are not "true". The importance of this is on leading and trailing edges while sanding. I always have tried to purchase the best blocks I can find. It just seems they are not to my expectations. This is important because of the amount of material you may remove. This is based on the 3M hard block. Understanding with a hard rubber block you are removing material at a greater rate than a soft block.

No block is true.

Lets start with a brand new block,

Here i have made a few passes over a block over a peice of 180 sand paper across a 1/4 in. piece of glass with 180 stick it 3M. The dull spots indicate the high spots. The shiny spots are the lows sanding with this will create waves in the panels.

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you can see the low spots here.

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You need to continue while holding on to the sides while removing residue to keep the block flat, Rolling rubber will not true the block. Constantly clean residue.

This is further along in the process you can see the low spots the final picture gives a trued result.

NewPictures003.jpg



I'd like to add here take the paper and round the edges to prevent
"checking" where the paper may grab and create a groove while sanding
NewPictures004.jpg
 
While this may not seem to important at first it makes a great importance on how you are removing a defect or leveling paint. It is very possible to create waves with a block that is not level. The best correlation I can relate to is go to Lowes or Home Depot and look down their 1x4 or 2x4 stacks. how many end up on the floor before you find a straight one. It is trult the same with moulded rubber sanding blocks.
 
Absolutely great advice Mr. Concours. I had the pleasure of watching an extremely known body shop 'truing' their paint long blocks in preparation to block sand the base coat of a car. It was absolutely amazing, they check the trueness with laser guides.

Of course the work they do is beyond anything I have ever seen. 100s and 100s of hours in the body, a little body filler if needed, allowed to cure for months (in the case a '66 Shelby, years), block sanded, and re shot. They long block the base after every two coats, then block the first four layers of clear before adding 4 more. Then the cars are parked in the desert for 1-2 years to allow everything to shrink, before behind long blocked again, then finally hand sanded, cut and buffed. I believe their paint jobs are known to cost into six figures and take years. It's really cool to see how far people will go to when they raise the bar of every process.
 
Todd Helme said:
Absolutely great advice Mr. Concours. I had the pleasure of watching an extremely known body shop 'truing' their paint long blocks in preparation to block sand the base coat of a car. It was absolutely amazing, they check the trueness with laser guides.

Of course the work they do is beyond anything I have ever seen. 100s and 100s of hours in the body, a little body filler if needed, allowed to cure for months (in the case a '66 Shelby, years), block sanded, and re shot. They long block the base after every two coats, then block the first four layers of clear before adding 4 more. Then the cars are parked in the desert for 1-2 years to allow everything to shrink, before behind long blocked again, then finally hand sanded, cut and buffed. I believe their paint jobs are known to cost into six figures and take years. It's really cool to see how far people will go to when they raise the bar of every process.
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Oh my God, that is crazy! I'd imagine the end result for these jobs would be well worth the six figures for the right car and collector. Although they're probably not who I'll go with when my wife's Civic needs repainting.:D
 
Thanks Guys,
This is just something that suggested many years ago. It has made a huge difference in leveling primer before paint and clear after.
It will level faster. You will not chase the lows in the paint from the high spots in the block making contact first. The end result is removing less clear or paint to get it level.

Todd,


Todd Helme said:
Absolutely great advice Mr. Concours. I had the pleasure of watching an extremely known body shop 'truing' their paint long blocks in preparation to block sand the base coat of a car. It was absolutely amazing, they check the trueness with laser guides.

Of course the work they do is beyond anything I have ever seen. 100s and 100s of hours in the body, a little body filler if needed, allowed to cure for months (in the case a '66 Shelby, years), block sanded, and re shot. They long block the base after every two coats, then block the first four layers of clear before adding 4 more. Then the cars are parked in the desert for 1-2 years to allow everything to shrink, before behind long blocked again, then finally hand sanded, cut and buffed. I believe their paint jobs are known to cost into six figures and take years. It's really cool to see how far people will go to when they raise the bar of every process.
Click to expand...

I was fortunate to start out in a high end restoration outfit. I was taught this before being responsible for final blocking and paint finishing.

Many of the processes you mentioned were used. (we had no desert) There is time needed between steps. This explains why some restorations take years.

This process lead to a Dakota Red with white interior 57 Eldorado Brougham receiving "Most Oustanding General Motors Car" at the 2004 Amelia Island Concours along with every other detail perfect.
It is probably the most winning vehicle to date I had the pleasure of working on.

The extra time pays off on little details such as a block being true.
As always practice, you will see the difference. I hope this helps.
 
Great post John! It's the attention to details that really make the difference. I'll have to do this to all my old blocks
 
C. Charles Hahn said:
Do the pics John posted not load when you look at the thread or something? :inspector:
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Duh...

I get it now. He sanded the block true using a glass plate as the standard for trueness (a new word I just made up).

It was late and I was tired, my only excuse :redface:
 
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