Regarding Sandpapers

Wet sandpaper is usually silicon carbide or aluminum oxide abrasive and is attached to backing with a waterproof resin bond.

Used with water on models (kubricant I guess) it gives smoother finish. Also used in sharpening tools (with oil) or if item is wet (sanding outside in the rain).

Usually sold as wet/dry since it is also used dry like normal sandpaper if need be.

Dry sandpaper won't have waterproof bond for grit and would turn into a mushy mess if used wet. It is cheaper and fine for general use on wood, etc.

Another thing nice thing about wet sandpaper is that it keeps down the sanded particles, controlling mess and helping prevent you from breathing that junk into your lungs. It is always best to use a dust mask when doing any kind of sanding, although I must confess that I'm poor in keeping to that safety process.

If you are sanding resin parts, this is particularly important. Resin dust is toxic! Those who build the resin ship models should keep this in mind.

Bill Shuey

I've taken to doing my resin figure clean up stuff out in the backyard. Not sure if it helps but at least I'm not in an enclosed room.

Craig

I repeat for about the hundredth time since the first of the year, resin dust is NOT toxic!!!! It is a pure and simple mechanical hazard and is no more or less dangerous to you than common baking flour or dryer lint ground very fine and atomized, in fact it's less dangerous as it has a much higher flash point than flour or dryer lint. While you may have a sensitivity or allergy to resin dust that does not make it a toxin, uncured resins on the other hand are toxic, once cured they aren't. You can also be just as sensitive or allergic to flour or lint. Sawdusts from some exotic woods are toxic, it's the oils in the wood not the wood itself, I'd be much more careful sanding rosewood, coco bolo, any nut wood, any tropical wood and anything from an orchard than I would be with resin.

AGA> If you are sanding resin parts, this is particularly important. Resin

Hmmmm... I was just wondering... I've heard resin dust is toxic. Can anyone tell me if it is? ;-) Hehehe... Haw, haw haw... Hah! Hack! Cough, gag.... wheeze... . .. ... Sorry Ron, I couldn't resist...

Frank Kranick

R> I repeat for about the hundredth time since the first of the year, resin

It may not be toxic, but it will make you impotent.

Wildat wrote concerning resin sanding residue:

does that me you get to wear the tuban and cape AND get to set at the head table of the lodge?

Rick MFE

and such?>>

This may sound simplistic, but the difference is that you use one strictly dry, the other can be used wet or dry. Without getting into the chemistry of it all, dry sandpaper is your average stuff for sanding wood. The paper itself is typically light tan. The adhesive that holds the grit is water soluble, so if you attempt to use it wet it thw abrasive will basically wash off. Wet-or-dry sandpaper has a non water-soluble adhesive, so the abrasive stays on. The paper itself is typically dark gray or black, and will specifically say "wet or dry". I don't believe I've ever seen regular dry sandpaper down to the microfine grits you'd see on wet or dry. Therefore, wet or dry is designed to get surfaces VERY smooth, to the point of being polished. Actual wet or dry sand 'paper' usually stops around 2000 grit, then finer grits, down to 12,000 are usually cloth-backed (someone feel free to correct me if I'm wrong on that point). Used wet, abrasives give a smoother finish in general, and it's best to use them under running water if possible because the particles are washed away immediately. For resin it's pretty manadatory to sand it wet simply because the particles are inherently dangerous to breathe. Hope all this helps.

Hey Osama, check your six

should read "Does this mean..." DOH!

Rick

I believe your description is universal. I just went to the hardware store and the colors are indeed consistent on the back. Tan color for dry sandpapers and gray to black for wet n dry sandpaper.

Although Norton/Bear brand also use a nice mid-blue colour backing on their

30 micron paper - get some if you find it, it's very fine (and also very useful).

RobG

Well, um...

I just bought a pack of K&S Flex-I-Grit labelled "Micro Fine Assorted" from my local model shop (Beaneys in Sittingbourne, plug, plug) It contains five plastic-backed sheets, of varying very fine grit sizes. I had to ask K&S how the sheet colours matched the grit sizes, and their reply was:

Green Chromium Oxide .5 microns Black Silicon Carbide 8 microns Dark Gray Silicon Carbide 23 microns Light Gray Aluminum Oxide 23 microns Tan Cerium Oxide 1.5 microns

(however, I think "Light Gray" is a misprint for "Light Tan", which better matches the colour of the sheet in my pack)

The backing sheet is clear and the binder seems to be colourless too, so I think the colours I'm seeing are the actual abrasive colours themselves. Certainly Cr02 is green, at least as far as I remember from my school chemistry lessons :)

As far as I can find out, 23 microns (particle size) translates to about

600 grit, and 8 microns to 1000 grit. So we are talking about polishing papers here! The provision of two types of 23 micron paper is interesting and prompted me to do a little research. It seems that Silicon Carbide is very hard (almost as hard as diamond) wherase Aluminium Oxide is softer (althought still harder than glass, for instance). This means that the Aluminium Oxide grains will blunt and break quicker than the Silicon, so the Silicon Carbide will leave more and deeper scratches. (although at 23 microns, we are talking about how cloudy it leaves your canopy rather than how deep the trenches are).

I'm not boring you, am I?

K&S can be found at

listed here seem to be a wholesaler, though. Many online hobby retailers list Flex-I-Grit; for example

Good info! Thanks!

The Keeper (of too much crap)

Assorted"....It contains five plastic-backed sheets, of varying very fine grit sizes Green--Chromium Oxide .5 microns Black--Silicon Carbide 8 microns Dark Gray--Silicon Carbide 23 microns Light Gray-- Aluminum Oxide 23 microns Tan--Cerium Oxide 1.5 microns

Ok, I stand corrected, rejected and ejected. When I said dry paper was tan and wet or dry was black, I was referring to the garden variety hardware store stuff, which is what Chad originally asked about. Now I'll throw a little confusion into the mix. The K&S set I have lists it this way--

600 ALO, 400 ALO, 320 SIC, 150 SIC, 280 Garnet. The package doesn't match colors with grits, but after a little touchy feely I think I figured them out. 600 is red, 400 light gray, 320 dark gray, 280 orange,150 black. FWIW, these also match the Testors pack, which lists colors and grits. All this talk about grits is makin' me hungry, and I haven't had breakfast yet, so....

When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return. --Leonardo Da Vinci

Ooops, sorry if I came across as heavy-handed, I only meant to add some more information into the mix. I think the most obvious way to tell wet&dry from dry-only is the backing: if it looks like it will break up when wet, its probably dry-only. And you are quite right, most general-variety hardware store sandpaper is sand-coloured.

For even more confusion; I have in my hand a store-bought pack of wet-or-dry *paper*. Made by 3M, the abrasive is black (Silicon Carbide, it says), but the backing is paper; printed with the words "Wet or Dry" and "waterproof". So, paper can sometimes be used wet (especially if it says so on the back).

I also have a pack of "Crocus Paper". This is dark red in colour, but not waterproof! However you are unlikely to find it in most hardware stores, I think. Googling I find that the term crocus is applied to Iron Oxide; so this is rust paper!

I think that you have their Regular assortment, like this one here:

Which, with grades down to 150, will be capable of changing the shape of your model rather than just polishing it! From th K&S literature I assuem that these sheets are also polyester backed and to be used wet or dry. My shop only had the Micro Fine pack, but that is what I wanted anyway.

I think the 600 grit Aluminium Oxide must have colour in the binder that holds the abrasive to the backing - an obvious way to tell the sheets apart. However, I have suggested to K&S that they put a reference list on their website, at least.

I think this exhausts my abrasiveness: sorry if I appeared to be rough with you :-P

150....my shop only had the Micro Fine pack>>

Didn't know there was such a critter, I'll have to take a look for it, thank you. Initially, yes, I thought your reply was a bit terse, but in retrospect, I realize it was unintentional, as was my comment. To all, FWIW, the company that makes the flexi-pads and cloth-backed sanding sheets/kits sold by Micro-Mark is in West Liberty, IA, and, and, I know they give away samples; samples being not just bits and pieces of the material, but square foot sections of any grit requested, and polishing kits as well for 'promotional purposes. I'll do some digging and see if I can come up with the name and address. If all else fails I could do a road trip I guess, it's about 60 miles from here.

When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return. --Leonardo Da Vinci