Hand Abrasives Round-up
3M’s Sandblaster sanding sponges and plain wet/dry sandpaper stand out.
Back in the May 15, 2001, issue, PS published the results of an exhaustive test of sandpaper. (Good times, good times!) We used 80-grit disks on a random-orbital sander with moderate hand pressure, and although we didn’t even bother to test the cheap paper—good sandpaper isn’t too expensive, and it’s infinitely better than the flimsy bargain stuff—after many disks and many hours, it was hard to choose winners. We picked three top papers: Carborundum’s Premier Red, Norton’s Blue (A975), and 3M’s Imperial. The Imperial earned the crown because it performed well on all five of our test surfaces.
Sanding big, flattish surfaces in a boatyard or dockside with an endless supply of electricity is one thing, but there are plenty of projects for which sanders can’t or shouldn’t be used—like sanding rounded, hollowed, or irregularly shaped things; smoothing corners and edges; scrubbing underwater; touching up small areas for revarnishing or painting, and so on.
Unless you take extraordinary measures, keeping sandpaper on a boat is just a pain in the neck. It tends to get soggy, curl up, stick together, shed its grit, and generally refuse to serve just when you need it. In recent years, woven plastic abrasive pads from 3M and others have elbowed sandpaper aside for a lot of hand-sanding, hand-abrading chores.
Several features about the woven pads stand out. They’re hardy and don’t shed grit. They don’t tend to load up with abraded material the way sandpaper does, although they’re not immune to it. They can serve triple duty for wood, metal, and paint. They’re good for light cosmetic metal work because they contain no metal themselves, and won’t promote rust as, for example, plain steel wool does if it’s used to take rust spots off stainless. They can be used underwater. And they adapt easily to life aboard the boat: no curling, no sogginess, etc.
These pads come in a huge variety of shapes, configurations, thicknesses, brands, and levels of aggressiveness. It would be folly to try a comprehensive test of even a modest fraction of them, head-to-head with various sandpapers and metal wools, using manual pressures and strokes, on several different surfaces. However, we thought it might not be folly to try a small representative test or two. Beyond that, the sensible thing to do was canvas a bunch of regular contributors to Practical Sailor, most of whom are marine professionals, and all of whom are competent tinkerers and do-it-yourselfers, asking how much involvement they have had with 3M-type pads, what they think the pads are best suited for, and where they come up short. (Other manufacturers make similar products, but we decided to stick with one company for this evaluation.)
The results of these interviews and experiments follow.
In our informal survey of contributors and experts, we asked what percentage of chores formerly tackled with sandpaper are now tackled with 3M woven pads. Answers came back all over the place, but in the final tally, it was somewhat less than 20 percent. Mostly, that lack of bandwagon-jumping was explained by phrases like “Old habits die hard,” and “If it ain’t broke, don’t fix it.” There was general agreement, though, on several items.
Not good for initial/tough sanding: The 3M woven pads come up short for initial sanding of rough wood, edge-sanding, and taking down tough irregularities.
Editor-at-large Nick Nicholson and Executive Editor Dale Nouse, both vastly experienced painters and varnishers, were asked for opinions on the topic. Nicholson said, “I’ve always felt that the sharpness of a fresh piece of aluminum oxide (AlOx) sandpaper—or silicon carbide, if you’re sanding metal—is impossible to beat, particularly when it comes to coarser grits. For fine sanding of bare wood or varnish, you can’t beat stearated (white) aluminum oxide paper.”
Nouse is of the same school of thought: “Despite using all of the various grits of these pads, I’ve never found one that was effective at sanding gloss varnish or semi-gloss or gloss paint. They work, but you have to push too hard to get them to cut. I put the pad aside and go for the sandpaper. For me, there’s still no substitute for the various grades of sandpaper. In the old days, I used to use fine forever, but now know that it’s better, easier, and quicker to use 80 grit, then 180, then 220, if needed.”
Other contributors concurred: “They’re not good for removing material.” “You need sandpaper to take down barnacle cement after the barnacle has been removed. The 3M pads just get torn up.” “If you really need to remove substrate, good sandpaper seems to work faster and cut deeper.” “The 3M pads don’t have sufficient heft to sand metal or very rough wooden surfaces.”
Good for sanding between coats: At Dutch Wharf, a small boatyard in Branford, Conn., known in New England and beyond for its meticulous refinishing and restoration work on wooden boats, Keith Johnson says that 3M pads are in constant use for certain purposes. “Like any other tool, they have their place. They’renot a substitute for sandpaper, but we use them all the time, especially the 7447 general-purpose pad. You wouldn’t use it for initial sanding, but it’s good for very light sanding between coats of varnish. It’s also good to use on an aluminum mast for an Awlgrip job. It gets around rivets and screw heads, and you get a nice bond and good adhesion. And these pads last a long time. You can reuse them—we have them all over the place.”
Up the coast at Brewer’s Pilot’s Point, a bigger yard also known for high-quality workmanship, 3M pads are used “for a light scuff on an Awlgrip job, because sandpaper is too aggressive.” They’re also used “fairly regularly to prep boot tops for paint,” and to clean and brighten propeller shafts before zincs are put on.
Another contributor said, “Paint prepping comes out cheaper. It’s a faster way to add tooth between coats.”
Good for aggressive cleaning: When considered for exactly what they are—densely gnarled plastic mesh—it’s easy to see why the 3M pads are well-regarded as cleaning tools. Contributor comments: “They’re good for getting at stains and mars, and for general cleaning beyond the capability of a sponge and soap.” “Excellent for sanding a dirty surface, like my outside basement door. I use them with soapy water. Scrub and rinse, and it’s ready for paint.” “I use them on my table saw surface to get rid of wood residue. This makes the wood slide better. You can’t really use sandpaper except maybe 600 grit, because you would gouge the table.”
Metal buffing/light derusting—Be careful!: As mentioned, the 3M pads do well at shining up a propeller shaft. They can also take spot rust off stanchions, handrails, and other stainless, but great care must be taken, because too aggressive a pad will scratch a shiny stainless surface. One contributor said, “I’ve been buffing lots of bronze lately, and the pads are too abrasive for this job. I use a buffing wheel instead. I tried using a 3M pad with bronze cleaner, but the cleaner ran through the pad and all over my hands.”
When distinctions are made between buffing, burnishing, and merely scrubbing metal, the pads show up in a better light. “I spend a half-hour at the beginning of each season working on my three-bladed bronze prop with a 3M pad,” said one correspondent. “It doesn’t really shine it bright, but it really smooths it, which helps keep barnacles off it.”
Good for bottom paint in and out of the water: On this point, sentiment was unanimous. When a boat is hauled and the bottom dry, a 3M pad does a fine job of abrading off the residue of old ablative bottom paint and any scum that may be on it. Running neck-and-neck with it, according to one contributor, is plain old drywall sandpaper, of the familiar black, open weave. It refuses to load up with paint, and is aggressive enough to do the job with a few hard swipes.
When the boat is in the water, the 3M pad works better and is easier to use than a bristle brush when taking off soft growth and scum. The pads are often sold attached to plastic handles, which are not to the liking of one contributor: “Those handles always fall off, and they actually make it a little harder to follow curves underwater. I just keep the pad against the flat of my hand, and it conforms better that way.” While racing purists using hard bottom paint might prefer the absolute silkiness that can be achieved by wet-sanding, mere mortals can get most of the way there with a 3M pad.
Of Blocks, Sponges, & Product Multiplicity
Never mind simple scrubbing—when you get into the subject of wood-finishing, passions soar. During our interviews, several people asked, “Are you going to cover sanding blocks, because they make a big difference.” On that subject alone, Nicholson had this to say: “Unless I’m sanding something rounded, like a handrail, I always block-sand with a firm block to keep the flat surface fair. I custom-make blocks of cork or lightweight 1/4-inch plastic. Even when sanding between coats of varnish, every third coat is block-sanded to keep the surface fair and take out brush strokes—not that I ever have any, of course! This is what gives a flat, varnished surface its really high gloss. I’m not sure that the synthetic (non-paper) sanding devices are really firm enough for surface fairing of this type.”
Meanwhile, others asked, “Are you counting those sponge sanding pads with the synthetic sandpaper that 3M makes? I use those all the time.” Or, “What about the really heavy-duty 3M stripping block?” Or, “Are you going to talk about the thick sponge block they make that has a synthetic all-purpose grit on four sides? That thing is good for sanding in corners.”
The Minnesota Mining & Manufacturing Co. makes a lot of products, and re-brands a lot of products. And others make products like theirs. We’ve included a portion of these products in the accompanying photos.
For our own edification—and putting out of mind the acres we’ve sanded over the years—we tried a couple of our own experiments. First, we used a sampling of eight likely abrasives on taped-off sections of a hollow-core lauan veneer door (that’s from Lawaan in Tagalog; the wood is often sold as Philippine mahogany) with six coats of spar varnish on it. We chose the eight to represent a wide range of types and levels of coarseness.
We took 50 strokes per section, using moderate hand pressure, and tried to get pretty close to the tape margins. The idea was to see the evenness, depth, and control of the abrasion. Second, we tried most of the same products on a sheet of teak-and-holly cabin sole veneer that we’ve mistreated over the years. On it were many miscellaneous stains, including oil, battery acid, streaks of paint where things had been dragged over it, and some red permanent marker, courtesy of a visiting 5-year-old. Note: Battery acid on teak-and-holly? Fuhgeddaboudit. Might as well just drill it out with a hole saw.
Hands-down, the product that impressed us most was 3M’s SandBlaster Sanding Pad (thin sponges on the back, synthetic sandpaper on top, series 20916-180 grit, 20917-100 grit, 20918-60 grit). We tried the 60- and 100-grit both wet and dry, and found them easy to use and very effective. The 60-grit version was the all-around favorite among the eight products we used on both the varnished lauan and teak-and-holly veneer, although the 180-grit wet/dry sandpaper ran a close second on the varnish, at least for smoothness and control. The beauty of the 3M pad is that you can load it up and rinse it out repeatedly, and find no loss of abrasive or reduction of power. We’ll keep putting these pads through their paces this summer and report back in a few months.
Among the woven pads, we were least impressed with 3M’s Heavy-duty Stripping Pad (10111), which is certainly a tough-looking customer, but very light and too “ventilated.” It seemed to abrade the user’s hands more than anything else. It might be good for deburring sheetrock and knocking irregularities off other softer material. We didn’t try it for those things.
The middle range of the woven pads can serve a myriad of uses—boat bottom cleaning, scuffing between coats, heavy-duty cleaning, and so on. For most of these chores, 3M name-brand and “marine-grade” pads are probably not necessary. If you can find a generic or re-packaged bargain at the grocery store or hardware store, grab it.
We’d like to hear from readers who have had good and bad experiences with these 3M-type pads and sponges, versus, or in conjunction with, sandpaper. There are, no doubt, more uses than those we have room to explore here. So send us your ideas and project notes. Elbow-greasers unite.