Wet Sanding

[zcarmannn]

I am planning on painting the hood of my car. I was told by someone that I needed to wet sand my hood before I paint it. Would something like this work?

http://www.autobodytoolmart.com/p-12829-15974.aspx

[gotswap]

Depending on the condition you could just grab some scotch brite to scuff it up.

To answer your question yes that would work or you could get a bucket of water with a normal sanding block and wet sandpaper.

[Mr Camouflage]

...and a sponge to drip the water/wipe the crud away.

[JimmyZ]

Easier to go down to your paint jobber and get something like the scruff block shown on this page...

http://www.dura-block.com/durablockline.html

They are made in many densities. You want a rigid block for straight/flat surfaces and a more "spongy" block for curved surfaces. The reason not to use a block that is too rigid is that you might inadvertently sand a flat spot.

These blocks are made by 3M, durablock... you name it. All you do is simply cut a sheet of 400 or 600 grit in half and wrap it around the block. Have a hose with the metal end cut off flowing water over your sanding area. (Hose w/ metal may ding or scratch surface) Keep the paper well rinsed so that there's no buildup otherwise you will cut gouges in the paint. Check the paper often and run your hand over it to clean any buildup off. be sure to have the surface well cleaned from both debris and wax/grease. Use wax and grease remover prior to any sanding or painting.

Finally there's no need to buy that fancy piece of ____ as shown in the picture. People have gotten along without it for ages.

2c

Jim

[Travel'n Man]

My '72 is on its last of a year long mission to the body shop (one year, three days and counting). I was there this morning and the tech's were wet sanding. They had a bucket of water keeping the surface wet along with keeping the spent material out of the wet sandpaper. They were sanding doors and were not using a block. The car had already been blocked several times with a guide coat of black over the primer. The black guide coat gets blocked off to show the highs and lows and what and where needs more attention. The final wet sand should only be a very fine finish layer to make everything smooth.

I hope that helps.

[EScanlon]

The dura-blocks are excellent for those who have a hard time using the edge of their palm AND keeping it in mind that they must be careful not to "groove" the surface they sand. There are different styles, shapes and lengths. I have several and each has it's purpose and size of sheet it uses.

The block with the included water hose is a "cute" idea, but you can duplicate that effect by simply hosing or taping a hose above the panel as you work. For 21 bucks, you could probably pick up a couple of the dura blocks. The only advantage I can see to that set up is that you wouldn't have to refill your drip bottle (I use an old salad dressing plastic bottle with the reduced hole cap) or continuously reach down to re-soak your rag or your sponge. I can't imagine how messy it would be as you sand though.

FWIW

E

[five&dime]

You don't need to wetsand prior to painting. The only wetsanding I do in post paint is wetsanding primer with 600 and then the first two base coats with 800. This is only for a perfectionist job and only when I am down to metal. You don't want to wetsand the final basecoat before clear either FYI.

Wetsanding is mainly used for post work. When I clear a car I wetsand with 1500 and then 2000 wrapped around a 3M foam block. Then I high speed buff at 3000 RPM using 3 pads and 3 different 3M products. I wetsand with 600 only if I have runs in the clear and then work my way up to 800, 1200, 1500 and then 2000.

If you are just prepping for paint and your old paint is decent, then all you need to do is get a 3M scotch bright pad and scuff the surface. You want to eliminate all the sheen from the finish trying to cut through as much clear as you can. Then just wipe the surface with pre-cleaner, wipe it with a tack cloth and then you are ready to shoot.

Edited October 15, 2008 by Zero Z

[jtl260z]

I am planning on painting the hood of my car. I was told by someone that I needed to wet sand my hood before I paint it. Would something like this work?

http://www.autobodytoolmart.com/p-12829-15974.aspx

The wet sanding process should take place after painting.

Listen to Zero Z. He knows what he is talking about.

[five&dime]

FYI: When I wetsand I either just hold the hose over the surface as I go, or I use a spray bottle and just constantly mist the surface and the sandpaper.

You only need to wetsand prior to painting if you are going for a show paintjob. Even at that rate it should only be used on primer/paint that has been layed down fairly recent. If you were to wetsand the old surface prior to painting for just a simple panel paintjob, it would take you forever and is pointless IMO. Wetsanding only removes a minuscule amount of material. You need to be careful when wetsanding a finished paintjob as it is fairly easy to cut through the clear coat when you get going. When that happens you have to start over

It took me almost 7 hours to wetsand and buff just the driver side of my 510.

BTW, if it doesn't look like the 3M pads are sanding enough or there are a lot of pits. try 400 and/or 600 gritt. Just use light to medium pressure though. If you sand too hard it will be a nightmare to get the sand marks out. You generally have to sand twice as long each time you go up in gritt to get rid of the previous gritt marks. For instance. If you sand one area for 10 minutes with 400 then you want to sand that area 15-20 minutes with 800 etc.

[Kiwi ZX+Zed]

after 20yrs in the paint biz,i agree with all of Z's comments.

A good hint is to hold a sponge over your panel to keep the "Slops" off it,just keep rewetting the sponge in a large bucket of water....comes in handy when youre wet-rubbing at 7am when its close to 0deg C outside,boil the jug empty into your bucket and enjoy warm hands.