In the last installment of this series, I explained how to rejuvenate antique finishes that are still bonding well to the wood. But for antiques where the finish strips off during the cleaning process, you’ll need to refinish the surface.
Removing the finish
Removing the finish is a time to truly embrace a Zen way of life, for it can be slow going. Paints tend to be harder to remove than shellacs, lacquers, and varnish; they have more solids, which don’t dissolve easily, and they were often applied repeatedly, so man¬y layers may await you. For the sake of your own health, and the environment, I urge you to try water-based strippers. They work well if you apply them thickly, and you can keep them from drying out by covering your work with a layer of clear plastic. This not only retains moisture to keep the stripper active longer; it also allows you to observe the “lifting” of the finish—a sign the stripper is being effective.
Occasionally lift the plastic and using a putty knife or plastic scraper to see if the film gives way. If it’s doing what it should, then you can employ many “tools” for removing the slimy film. Coarse brushes, including toothbrushes of various sizes and even coarse cloth, will help you clear the surface of the wood. Avoid using steel wool with water-based products, or you’ll be dealing with rust stains next. An abrasive plastic cloth like Scotchbrite is ideal for scouring the surface, and it comes in a range of grits.
Cleaning the surface
When you’ve removed all you can, you need to rinse the surface with clean water. Just don’t drench the piece, or water could get into old joints held fast with hide glue, and they’ll start to soften. Make certain to allow the wood to fully dry before attempting sanding. There will always be those stubborn finishes that don’t respond completely to chemical removal, and then you must sand and scrape. A word of caution: many old paints contain lead, and if you’re going to sand, you need to take precautions against lead dust. Wear gloves and a particulate filtering mask, and be sure to¬ clean your dusty workspace and clothing prudently. If available, dispose of lead dust and paint chips at a hazardous materials facility.
You now have a clean piece free of finish residue, and are ready to proceed with the next step in preparing for new finish.
Sanding the original finish
Sanding is a potent tool in the woodworker’s arsenal; understanding it allows you to achieve better results. Most furniture endeavours use sandpaper from 60 to 320 grit. Think of the grits as the number of particles per square inch—the lower the number, the larger and coarser the “sand,” and vice-versa.
Deciding which grit to start with takes practice, but here’s a place to start. I would avoid using coarse grits like 60X and 80X to smooth surfaces, as it takes a lot of focused effort to remove those deep scratches. That’s what sanding is all about: making progressively finer scratches on the surface of wood or finish until you can no longer see them. There are also many different types of papers, but a common aluminum oxide abrasive on paper backing should prove effective for preparing surfaces for finish.
On stripped objects where you will be working to achieve a smooth surface for new finish, I would start with 100X, being careful to keep your sanding scratches parallel to the wood grain. This makes them that much more difficult to see because they mimic striations in the grain of the wood. If you must sand across the grain, just be sure to follow up with finer grits until you don’t notice the scratch lines anymore. On a table, for example, I would sand the structure all the way to 150X, and the top to 220X or even 320X.
After each sanding with a given grit, remove all dust and abrasive particles so as not to contaminate the next finer grit. So start with 100, then 120, 150, 180, 220, and finish with 320. There’s no shortcut in skipping grits, as you’ll just have to sand more with a finer grit to remove prior scratches.
The key to achieving stellar results is to be thorough and careful in observing the surface between grits. Good lighting is paramount here. It sucks to get to the stage of applying finish, only to discover a coarse scratch you missed.
One other quick note here that goes just a bit beyond the finish, but impacts surface quality greatly: on many production pieces of furniture, the machined edges are not eased; that is to say that they are sharp and not rounded over at all. This type of edge is very vulnerable, and you will spot it on pieces when you notice little chunks missing along the edges of legs and rails. All it takes is a bit of sanding with 100x or perhaps even 80X for large damage, and you can blend in the damaged edges and ease all of the others so that the sharpness is no longer an invitation to future chipping. Simply hold the sandpaper surface against the corner or edge and move side to side until the degree of blunting is desired. If you do have to use 80X, be sure to follow up with 100x.
Applying the new finish
Once you’ve stripped and prepared the wood surface, it’s time to decide on a new finish. Shellacs and lacquers were the original finishes, but we’ve largely moved away from them, as they are not very durable—you can often recognize them by the white water marks on their surfaces. Lacquers are outlawed in many jurisdictions due to their nasty solvent content, and even oil-based paints are getting the boot in favour of water-based finishes.
Water-based finishes have really come into their own of late, with products that apply like a dream and outperform their solvent-based counterparts. Again, give yourself and the environment a break, and go with a low VOC water formula like any of the superb clear coats by Sansin. You will be impressed with how easy it is to use water finishes, and at how great a surface you can achieve.
One of the quirks of water finishes is that they will raise the grain of the wood slightly after the first coat is applied. This is just the remaining wood fibre from sanding being made to stand up due to the introduction of water and the subsequent drying of the finish. At this stage, some 220X paper will easily knock down this bristly surface, leaving you with a smooth place to commence your next coat. Take time to remove the dust between sandings by using a damp cloth. The old-style tack cloths should not be used before a water finish, as they can leave behind oily residue.
If you want to introduce color to the finish, consider having the clear coat tinted rather than using stain. This gives you the opportunity to sneak up a bit more on the colour, as each coat of tinted finish will increase the intensity. It’s nearly impossible to alter the colour of stain once it’s soaked into the wood surface, and many purists think it has no place on furniture, especially antiques. The colour of a piece can be altered in the future by stripping the topcoat, whereas stain is a lot like a tattoo—once it’s skin deep, wanting to change it is very difficult.
To finish the job, apply finish with a brush, stain pad, or sprayer, taking time to sand lightly and dust well between coats. I would suggest at least three topcoats.
Sean Ledoux is a designer/master fine craftsman working with wood and other found media to create unique furniture. Restoring antiques helps support studio life in North Bay, ON. www.seanledouxfurniture.com