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Dry or wet block sanding...???

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BrotherBamc View Drop Down
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    Posted: Sep/22/2018 at 12:23pm
Well, I am to that point in my build that I have to decide whether I want to wet block sand or dry block sand the final coat of high build primer before paint. 
I've watched quite a few youtube videos, but really no definite answer to my question(s). Most if not all are just "this is how you do it" type videos. 
I have been dry block sanding everything so far and things are looking really well. Been using 400 grit to get what dirt and orange peel off. (and bugs Ouch) Dry block sanding has been kind of a mess and anyone that has done this will know that. The stuff gets everywhere and on everything. 
My question(s) are these...
Is there a real difference between wet and dry block sanding..?? 
Should I continue to dry block sand or should I wet block sand before final paint...?? 
Is there really a difference or a preference between the 2..?? 
If I do decide to wet sand should I use like a 600 grit for wet sanding since I've already done 400 dry..?? 
My "plan" is to use 2 stage base coat/clear on the outside of the car and use a single stage on interior, engine compartment and underneath the car. Painting will not be done by myself as I have found a paint booth and a painter to do the dirty work. I've been doing all of this in a small garage and there isn't enough room for the car and all the attaching body parts to be spread out. I can either work on the body of the car, or I can work on the doors, hood, fenders.
I would think that wet block sanding will give a finer finish and you wouldn't have as deep as scratches as you would with dry block sanding. 
Comments welcome...!! 
Thanks in advance...!! 
William 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmaher94087 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2018 at 12:40pm
Some folks like dry block sanding using the light from fluorescent lights to show the flaws. I preferred wet blocking as the water flowing across the primer acted like a mirror and showed the minute irregularities. It is very messy and the sanding dust will stain a concrete floor. Hint: wet the floor before starting to sand. 400 grit wet or dry paper will give enough 'tooth' for the top coat to adhere.
Mike
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2018 at 12:47pm
The prep is really about the painting.
So the question is what have you got for a paint both?
Unless you have a high end paint booth with filtration, air flow and baking, your spending a lot of time in prep that won't show in the final product.
If not doing the highest end paint job, I'd stick with the dry sanding and tack cloth.
The wet sanding acts as a lubricant to clear minute particulate and does make for a better prep - for the perfect paint that will show any minute imperfection.
It's all about the complete process and not one aspect. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote BrotherBamc Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2018 at 2:57pm
The paint booth is a high end booth. I am having Lewis Clark State College paint the car through their autobody and paint course. Students won't be painting, though the students may help with small things that will probably need to be done. The painting aspects will all be done by one of the professors and I'll be there for support. 
That's one of the problems that I have is my lighting. I have mixture of L.E.D. lighting and florescent. Probably not the best, but you do with what you have. I got an estimate on the paint that I'd like to use and I am looking about 1,800 bucks. Now if I was to "cheap out" on the paint, I could get everything for about 600 bucks. I'm not going that route. I've got so much time, efforts and money in this I might as well go big or go home. 
I think that wet sanding for final prep will be the way that I go with this. I still have some stuff to do on the body, but the doors, hood, and fenders are ready for final prep. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tyrodtom Quote  Post ReplyReply Direct Link To This Post Posted: Sep/22/2018 at 3:43pm
I prefer wet blocking whenever possible.

Cheaper because the paper doesn't fill up and end up putting deep scratches in the finish,  unless you change the paper often.   
And much healthier for you,  even if you're taking the precaution of wearing a mask,  some is getting by that mask.  And that sanding dust is settling on every surface in the area.

When dry sanding unless you blow the surface off very well,  and use a top quality tack cloth,  you're leaving loose sanding dust on your finish and priming over it.

A previous poster remarked on wet sanding residue staining the concrete,  well, just think about what that same dry dust can do to YOU.

   I've been doing this now over 45 years,  i'm one of the very few of my generation locally to make it to my age  ( 71)   maybe some of the reason is because even from the beginning I put some thought into what the products I was using and how to protect myself long term from them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mixed up Quote  Post ReplyReply Direct Link To This Post Posted: Sep/23/2018 at 12:19am
my preference on paint prep is cut in all line with 320 dry then the final is done with wet sand it help wash all the dust out of all the nook and crannies let air dry I do all my own paint so most of the time m final sand is done the day of paint to help from getting any oils on the surface a another trick I do is put a few drops of dish soup in my water it help in getting the paper to glide when our sanding don't be afraid to change the paper often a paint job is all in he prep     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mmaher94087 Quote  Post ReplyReply Direct Link To This Post Posted: Sep/28/2018 at 9:07pm
Either tape the piss out of the brass connector or cut the infernal thing off the end of the hose. With the water running in a small stream and holding the hose in the non-sanding hand above the area to be sanded; work from the top to the bottom of each panel. When wet sanding curved panels, like the top of the front fenders, sand diagonally. Front-to-back or top-to-bottom sanding will leave flat spots in the primer. The quality of the finished paint will be directly correlated to the quality of the primer surface and the prep work that is done to it. Don't expect the paint to "fill the scratch"; it won't. A finished coat of paint will only mimic and accentuate what is below it.
Mike
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