Lose The Sandpaper, Grab The Razor

By Scott Wunder | Posted: 11/24/2013 11:56AM

 

Scott Wunder Wunderwoods One of the best finishing tips I’ve ever picked up came from an episode of “This Old House.”

Norm and Tommy were building some cabinets for a house, and they were spraying a lot of plywood. They showed how they used a razor as a scraper to knock off the nubs between finish coats. It looked simple, so I gave it a go, and I haven’t looked back since.

razor edge for woodworking scott wunderHold the razor almost vertical and then lean the top the direction that you push. After about 3 seconds you will get the feel. Let me first start by saying that the razor isn’t perfect. It is flat and straight, so it doesn’t work for profiled edges or rustic, wavy surfaces, but it is great for big, open flat spots. I use it most often on sheets of plywood, but also use it on the flat spots of doors, including the stiles and rails.

The beauty of the razor is the simplicity and speed. With one razor blade, I can quickly smooth a surface between coats on a job that would eat up several sheets of sandpaper. The big difference is that the razor doesn’t clog up with finish like sandpaper does, it just scrapes off the high spots. This is especially helpful when I am trying to finish a job in just one day (which is usually the case). As long as the finish is set up enough to handle, I can start scraping with a razor and never have to stop. In the same scenario with sandpaper, it would clog almost immediately causing me to use more sandpaper and not get consistent results. The clogged sandpaper also tends to drop off little boogers of coagulated finish that stick to the surface. That never happens with a razor.

Using the razor is simple. Hold it up nearly vertical to the surface, lean the top into the cut and pull or push the direction you want to go. It works just like a cabinet scraper, only on a smaller scale, and it doesn’t need to be sharpened. When the razor is dull, just grab another one and move on. I often flip the blade around and cut the opposite direction to make the edge last even longer. If it feels like it isn’t cutting, flip it around. If it still isn’t cutting, just grab another one and get back to work.

Quick tips for using a razor:

  1. Make sure the finish is dry before scraping.
  2. Make sure runs are super dry before scraping. The finish should scrape off in shallow layers, not rub off in big chunks.
  3. Always use a new razor. Old razors can have nicks that scratch the finish.
  4. Use a razor on flat surfaces. Razors do not work on profiled edges.
  5. Watch the sharp corners. The corners of the razor can easily scratch the finish.
  6. Use a light pressure to start. Apply more pressure as you get more comfortable.

If you are going to be doing a lot of scraping, I highly recommend wearing gloves or putting tape on the top of the blade to serve as a handle. The blade gets hots and starts to dig into your hand during heavy use, so it is best to make it as comfortable as possible. There are plastic blade holders commonly available as well. They work fine, but they got lost easily. It seems like I can always find the blades (mostly because they came in a jumbo pack), but I can never find the holders.

As I mentioned, the razor is great for flat surfaces, even curved, flat surfaces (what?). Yep, that’s right, the ol’ curved flat surface, like the belly of an arch. The razor will work on a surface like this, as long as it can sit flat. You can still follow the curve by changing the angle of the blade and quickly scrape the surface.

The razor is not a good choice for profiled edges. First off, it often can’t reach where it is needed, and secondly, there is a great risk that one false move might destroy an edge. In this case, sandpaper or a Scotchbrite pad is the poison to pick.

I use the razor between coats of sanding sealer and even topcoats, when necessary. It makes for a speedy job and a quality one at that. The razor takes off only the highest finish, which is usually just dust nibs and other loosely clinging items (like the legs of flying insects). And, with a little extra pressure a razor will dig in deeper to help remove runs and other problems, like finger prints, smudges, etc.

When you use a razor for scraping a finish, watch the edges of the razor and your pressure. The edges of the razor are sharp and can easily leave an errant scratch. Use a light touch, so if you bump the edge into something it won’t plow a line through it. The lighter pressure also ensures that you don’t take off any more than the imperfections. Only apply more pressure after you get the hang of it and when you really need it.

Lastly, make sure to use only new razors. A razor that has even just one ding in it will scratch up the surface, and the scratches won’t show until the next coat is sprayed. Don’t be a cheapskate and try to stretch the blades you have. Buy a pack of 100 and rest easy knowing that you will use all of them, either for scraping or in a knife.

Using a razor on your newly applied finish will seem scary at first. Go slow, use light pressure and be careful. In just a few minutes you will get used to the feel of it. As you work, use your hand to feel the progress along the way, by rubbing the surface to feel for imperfections. Your hand will tell you what you’ve missed and where you need to work a little more. Give it a try, and after just one swipe of the razor, I think you will be hooked.


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About the Author

Scott Wunder Wunderwoods

Scott Wunder

From felling the trees through installation of the final piece Scott Wunder, owner of WunderWoods in St. Charles, MO, shares his woodworking knowledge with anyone that will talk to him about wood. Whether you want to learn about milling lumber or need help on a project, get your fill of woodworking infotainment at WunderWoods.com. Scott writes about all aspects of woodworking and specializes in finishing (mostly because no one else likes to sand). Scott can be reached at wunderwoods@sbcglobal.net. Check out Wunderwoods' website at Wunderwoods.com.

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Ron Wolfe    
Oharco Distributors  |  February, 17, 2014 at 12:05 PM

Been in the coatings industry 35+ years and concerned this article could lead to intercoat adhesion failures. Today's catalyzed coatings build excellent chemical resistance quite quickly and sanding between coats is not used solely for defect removal but more importantly to create a small surface profile for subsequent coats to adhere to. Ron Wolfe, Wood Finish Product Mgr, Oharco Distributors

Bernie Bottens    
La Center, WA  |  February, 18, 2014 at 10:23 AM

I would agree with both of you. First, I use the blade from a utility knife as a scraper all the time. It's one of my little things that I do in the shop because it's simply the right tool for the job in certain circumstances. While building a kayak several years ago, I was faced with needing to butt join some 1/8" plywood and then face that joint with epoxy and cloth. To keep things as flat as possible yet not sand through the face ply, I did a lot of scraping on that project. While finishing, I use the blade to remove an occasional run, a bug, or some other piece of trash. But I always feel the need to scuff that spot afterward to give the whole surface the same "tooth." That helps hide the blemish. I spray mostly post-cats and pre-cats that must be sanded between coats. I am really anal about scuffing because I know what doing otherwise causes. Using a blade to remove a run or sag is the best approach. But one needs to wait until the coating dries all the way through. Otherwise, the blade tears at the soft material underneath and you create a bigger mess. The cure becomes worse that the cause! So since you have a sharp blade in your hand, angle it over until the bevel of the blade snaps down onto the surface. Voila! Now you have a mini low-angle plane to use to remove some of that over abundance of finish. Then things will cure out faster and you can scrape away the rest. In conclusion, I like the scraper approach for certain things because it gives me more control than sandpaper does. With every pass of the scraper, I can see where and how much I have removed. The "where" is the most important when you are trying to remove a bump or get to the bottom of a depression.

 

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