Dry vs. wet sanding

Is there any reason that PPG concept can't be sanded dry? I need to knock down some bad orange peel (because I'm still learning how to paint). I was thinking about using some 500 to knock down most of the orange peel, and then move to finer grits (wet) take out the sanding scratches before polishing. It seems like everyone is sanding wet, but why? It's much harder to see what you've done because everything gets covered with white goo. If I sand dry, I can blow the dust away and see what I've got immediately. I do know about guide coat and all of that, but I'm wondering what can go wrong if I make the first pass with 500 dry, and then switch to a finer grit wet?

Thanks,

John

On Monday, February 15, 2016 at 10:30:50 PM UTC-5, wrote:
Is there any reason that PPG concept can't be sanded dry? I need to knock down some bad orange peel (because I'm still learning how to paint). I was thinking about using some 500 to knock down most of the orange peel, and then move to finer grits (wet) take out the sanding scratches before polishing. It seems like everyone is sanding wet, but why? It's much harder to see what you've done because everything gets covered with white goo. If I sand dry, I can blow the dust away and see what I've got immediately. I do know about guide coat and all of that, but I'm wondering what can go wrong if I make the first pass with 500 dry, and then switch to a finer grit wet?

Thanks,

John

Your health would be one. During dry sanding isocyanates will be released, regardless how old the paint is. The newer the paint the more isocyanates will be released. You risk developing asthma, not really good for pilots . PPG Concept is a great paint but it requires proper precautions.

Additionally, most materials are better wet sanded to NOT build up stuff in the paper grit. This (buildup) can lead to scratches (even gouges) in the surface.
The water helps float removed material away and provides a small amount of heat dissipation.

If you want to "check your work", an inexpensive red rubber squeegie works well to make the surface dry again (as well as helping remove "sanding sludge").
The dry surface you're left with makes it a lot easier to look for "shiny" vs. "dull" to see where more sanding may be needed.

I wouldn't wetsand a lot of "natural materials" (wood, paper, bamboo, leather) unless they had a coating of something or were sealed.

Apply a Red disclosure coat then wet sand and you can immediately see
where you need to sand and where you have sanded enough... Sanding
wet extends the paper life and tends to prevent it clogging... Use good
quality paper (in UK Mirca is good)... Maybe start with 400 or 600 and
stop just before the last of the orange peel is gone... Then apply more
red disclosure and shift to 800, then 1200, then 1500.. Polish with
Farecla G3 then Wax... Craig...

At 05:24 16 February 2016, Charlie M. UH & 002 owner/pilot wrote:
Additionally, most materials are better wet sanded to NOT build up
stuff in
the paper grit. This (buildup) can lead to scratches (even gouges) in
the
surface.
The water helps float removed material away and provides a small
amount of
heat dissipation.

If you want to "check your work", an inexpensive red rubber squeegie
works
well to make the surface dry again (as well as helping remove
"sanding
sludge").
The dry surface you're left with makes it a lot easier to look for
"shiny"
vs. "dull" to see where more sanding may be needed.

I wouldn't wetsand a lot of "natural materials" (wood, paper, bamboo,
leather) unless they had a coating of something or were sealed.

On Monday, February 15, 2016 at 10:30:50 PM UTC-5, wrote:
Is there any reason that PPG concept can't be sanded dry? I need to knock down some bad orange peel (because I'm still learning how to paint). I was thinking about using some 500 to knock down most of the orange peel, and then move to finer grits (wet) take out the sanding scratches before polishing. It seems like everyone is sanding wet, but why? It's much harder to see what you've done because everything gets covered with white goo. If I sand dry, I can blow the dust away and see what I've got immediately. I do know about guide coat and all of that, but I'm wondering what can go wrong if I make the first pass with 500 dry, and then switch to a finer grit wet?

Thanks,

John

if you dry sand with 320 or finer, you'll sand for 10 seconds and your paper will be loaded/chalked up. you must wetsand young padawan. for wet sanding i recommend a plastic soda bottle with several small holes drilled in the cap. that allows you to use less water wit the same results. also, get a squeegee from lowes or walmart. that gets the surface clean and dry in seconds without all the mess. google "california water blade" and get that kind of squeegee, as you can clear a curved surface much easier, and check your progress more often.

-andy

On Monday, February 15, 2016 at 10:30:50 PM UTC-5, wrote:
Is there any reason that PPG concept can't be sanded dry? I need to knock down some bad orange peel (because I'm still learning how to paint). I was thinking about using some 500 to knock down most of the orange peel, and then move to finer grits (wet) take out the sanding scratches before polishing. It seems like everyone is sanding wet, but why? It's much harder to see what you've done because everything gets covered with white goo. If I sand dry, I can blow the dust away and see what I've got immediately. I do know about guide coat and all of that, but I'm wondering what can go wrong if I make the first pass with 500 dry, and then switch to a finer grit wet?

Thanks,

John

Slow down.
Put guide coat on and start with 1000 or finer.
When you scratch it with rough paper you ensure you will need to do a lot more sanding with finer grits to get the scratches out.
You are also much more likely to sand through.
Sand very wet and use a squeegee to clear the gunk off.
Take your time Grasshopper.
UH

On Tuesday, February 16, 2016 at 6:12:51 AM UTC-8, wrote:
On Monday, February 15, 2016 at 10:30:50 PM UTC-5, wrote:
Is there any reason that PPG concept can't be sanded dry? I need to knock down some bad orange peel (because I'm still learning how to paint). I was thinking about using some 500 to knock down most of the orange peel, and then move to finer grits (wet) take out the sanding scratches before polishing. It seems like everyone is sanding wet, but why? It's much harder to see what you've done because everything gets covered with white goo. If I sand dry, I can blow the dust away and see what I've got immediately. I do know about guide coat and all of that, but I'm wondering what can go wrong if I make the first pass with 500 dry, and then switch to a finer grit wet?

Thanks,

John

Slow down.
Put guide coat on and start with 1000 or finer.
When you scratch it with rough paper you ensure you will need to do a lot more sanding with finer grits to get the scratches out.
You are also much more likely to sand through.
Sand very wet and use a squeegee to clear the gunk off.
Take your time Grasshopper.
UH

Also use a block that's on the harder side. A soft sponge type block with fine grit sand paper will just shine up the undulations.

Cheers,
7Q

Yep......what Hank said! I use a 12 " Dura-Block with paper folded in half the long way. Wear gloves and dip the block in a bucket of warm water (to clear the residue.......warm to be kind to your hands). I do start with 800w after 24 hours at 70f. Comes off very easy while the paint (or gelcoat) is green. Buff it out after a week or so.
Have fun,
JJ

Thanks for the suggestions!

John

During dry sanding isocyanates will be released, regardless how old the paint is. The newer the paint the more isocyanates will be released. You risk developing asthma, not really good for pilots . PPG Concept is a great paint but it requires proper precautions.
------------------------

Can someone confirm this? I understand the dangers while polyurethane is
being sprayed, and perhaps also in the early stages of curing. But I
thought the material was pretty much inert after it cured. I haven't
been able to find any warnings beyond the spraying process on the
internet. Can somebody supply more information? I'd like to be as
safe as possible. Or at last understand the dangers.

Jim Beckman