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.
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:
- Make sure the finish is dry before scraping.
- Make sure runs are super dry before scraping. The finish should scrape off in shallow layers, not rub off in big chunks.
- Always use a new razor. Old razors can have nicks that scratch the finish.
- Use a razor on flat surfaces. Razors do not work on profiled edges.
- Watch the sharp corners. The corners of the razor can easily scratch the finish.
- 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.