One of the things that makes wood such a popular material is its resiliency. Oh sure, we all talk about its beauty and those of us who do woodworking as a hobby love how easy it is to work with. But it was the abundance of wood, coupled with the ease of working it and the resiliency of the finished piece that originally made wood such a popular material to build things with.
No material is perfect though; and wood isn’t perfect either. The things we make from wood can become damaged. Some damage is permanent and all but impossible to fix, like all the tables and chairs that get broken up in barroom fights in the movies. Other damage is superficial and can be repaired. Whenever possible, it makes sense to repair our wooden furniture from the damage it receives, allowing that piece of furniture to continue being beautiful and useful in our homes.
One of the most common types of damage that can happen to finished wood furniture is what are usually referred to as “heat stains.” These cloudy white stains mostly happen on lacquered wood, but can also happen on varnish at times, although that is rather rare.
Most commercially manufactured furniture is lacquered, rather than varnished. That’s because lacquer dries much faster and provides a very glossy surface finish, making the furniture look good. On the other hand, most homemade wood furniture is varnished, because lacquer requires spray application and most hobbyist woodworkers don’t have the capability of spraying lacquer. So this is actually a much more common problem on furniture that we’ve bought from the store, than it is for furniture that we’ve made.
What’s the Problem?
Before going any farther, let’s be sure we know what we’re talking about and how it happens. While this sort of damage is referred to as “heat stains,” it’s not really all about heat. Heat alone is much more likely to cause a burn mark, which is going to look brown to black. The damage we’re talking about here is caused by a combination of heat and moisture and looks milky white.
These stains happen because heat opens the pores in the wood, allowing moisture to get into the pores and the finish. As the wood cools, the moisture becomes trapped underneath the finish, causing the stain. So the trick to solving the problem is to get the moisture out of the finish.
By the way, moist can cause this to happen, even without the container being hot. It happened to an antique table that had belonged to my former mother-in-law. We were using it to hold the communion elements in my daughter’s wedding. Because it was a hot day and the wine was cold, condensation formed on the outside of the wine decanter, leaving this same sort of stain in the finish, as it is had been a hot bottle sitting on there. Fortunately, it was easy to get it out.
The Obvious Solution
The obvious solution to prevent this from happening is to use coasters and trivets. For some reason, these devices have largely fallen out of fashion, perhaps because so many people now own furniture that has surfaces which aren’t damaged in this way. Vinyl or laminate finish over particle board isn’t going to become damaged in the same way, unless the vessel placed on them is hot enough to burn the vinyl or laminate. Trivets can solve that problem too.
Any coasters that are being used for cold drinks should be absorbent, to prevent condensation from dripping onto the tale’s surface. That’s not necessary for hot drinks, as there is no condensation. In either case, it’s a good idea to have a soft material on the bottom side, such as cork or felt, to help prevent scratching the surface of the table.
Removing Heat Stains from Wood Furniture
There are a number of different ways of getting rid of this milky cloudiness in the finish. Different people swear by different methods. My take is to try one and if that doesn’t work, try another. Something is bound to take care of the problem. But before trying anything, allow the piece of furniture to sit for several hours, giving the moist the chance to make its way out of the finish all on its own. This is especially likely to happen in cases where the staining happened from condensation on a cold container, rather than because of heat.
Fix it with Toothpaste
The most common method of cleaning these stains off is with a combination of toothpaste and baking soda. The toothpaste needs to be a non-gel kind, which doesn’t have the abrasive quality that normal toothpaste has. Adding baking soda increases the abrasive factor slightly, helping to polish out the stain.
Before using the toothpaste and baking soda, be sure to clean the surface. Not only do you want to get any other spills and drips off of it, but you also want to get dust and dirt off which could cause scratching. Then make a mixture of the toothpaste and baking soda, rubbing it into the surface of the table with a clean, soft cloth, to polish out the stain. Work with a circular motion, cleaning off the toothpaste every few minutes to see what progress is being made.
Keep in mind that this is a polishing action, which means that it is an abrasive one. Some of the finish will be removed in the process. Care must be taken to not overdo the polishing action and remove all the finish.
Fix it with a Clothes Iron
The second method I see a lot is using a clothes iron. As with using toothpaste, it’s a good idea to clean the surface well, before applying the iron. Then place an old towel on the table’s surface to protect the wood from the iron. Set the iron to low heat and place it over the stain, moving it around as it heats the finish and the wood, allowing the moist to escape.
One danger with this method is that it can loosen the veneer, if the tabletop is covered with veneer (more likely), rather than being made of solid wood (less likely unless it is old or expensive). To help prevent this loosening, keep the iron moving around, spreading the heat.
If the heat alone is not enough to lift the stain, try using a small amount of steam, along with the heat. This will require heating the iron up further, increasing the need to keep the iron in motion. Use only a small amount of steam, through the towel, as too much steam can increase the stain, rather than eliminating it.
Fix it with Lemon Oil
Perhaps the easiest method of removing these stains is with lemon oil. Simply apply lemon oil to a clean cloth and rub the surface of the table, until the stain is removed. This ability of lemon oil to remove stains is why it is included as an ingredient in so many furniture polishes.
When All Else Fails
There may be times when the above mentioned ideas don’t work. The damage might reach too far down into the wood’s pores, rather than just being captured in the finish. In that case, it will be necessary to refinish the wood, rather than just remove the stain.
Refinish requires first removing the existing finish. This can be done either with a chemical finish remover or by mechanical removal. Chemical removers are convenient, but hard to control. If only the top of the table needs to have the finish removed, and the table has a carved or molding edge, the chemical remover will damage that finish as well. But that finish will be much harder to remove, due to the uneven surface.
Sanding is the most common method of removing finish from wood table tops. While the finish tends to gum up sandpaper, causing the use of a lot of sandpaper, it is a method that provides for a lot of control over how much finish is removed and where it is removed from. Just be sure to use the appropriate grit of sandpaper, so that not too much is removed. Take special care if the furniture is veneered, as most veneer table tops are only 1/40” thick, so it is easy to sand right through the veneer. If that happens, replacing the veneer is much more work.
As an alternative to removing the finish with sandpaper, a cabinet scraper can be used. This is a slow method, just like sanding, but it has the advantage of not plugging up the sandpaper. That saves money, while giving excellent results.
This same method can be used when the surface of the table is burnt, leaving a brown or black charred area. The risk of going through the veneer and into the underlying wood products is greater in this case, as the burn will probably be deeper into the wood, rather than just harming the finish. But it’s still worth trying to salvage the table by sanding through the burn, hoping there will still be good wood below that can be refinished.
In any case, finish sand the table with fine sandpaper, 320 grit or finer, then clean off the surface with a damp cloth to remove any lingering sanding dust. Then refinish the surface with at least two coats of varnish, sanding lightly with extra fine sandpaper between coats.