Friday, September 2, 2011

Stripping Patina?


I shudder to think about the way I approached refinishing furniture when I started over 40 years ago. First of all, I was young, impatient and considered myself indestructible. I was never sick, and could work all day and night, every day of the year. I was never tired and always excited to see what kind of wood was hiding under the disgusting old finish.

I consumed gallons of paint stripper, and went out of my way to use the stripper with the most methylene chloride content. It was more expensive, but, oh boy! did it work! Put the stripper on the surface and watch the dark years of dirt and finish wash away.

I was not too concerned about my exposure to the chemical. After all, I always worked outside in the shade with a cross wind and wore heavy rubber gloves. I really did not concern myself with a respirator, since it was always in the way, and I usually worked up a sweat. Comfort was important.

From time to time, I would get spots of stripper on my arms or face. Once even I got it in my eye. I would just turn the hose on myself and wash it off while I continued to work.

After about 10 years of this kind of activity, I started to notice problems. In fact it was my wife who would look at me when I returned home and say "I see you stripped furniture today." She could see the gray color of my skin and the confusion in my eyes. Methylene chloride had beaten me, and I started to question my whole relationship with the chemical. I began to research the material to find out what was going on.

I discovered that the chemical industry had a very effective and strong lobby in Washington to protect the use and distribution of methylene chloride. It was the most effective chemical to remove paint, and, for example, when you have to remove tons of paint from airplanes or ships you do not have a lot of alternative choices.

My good friend, Michael Dresdner (finishing expert), adds: "Futhermore, it's used in a host of other manufacturing operations, including as an aerosol propellant, a plastic welder, a blowing agent for urethane foams, a degreaser in electronics manufacture, and to decaffeinate coffee, tea and create flavoring and hops extracts. One of the more interesting marginal uses is in those bobbing glass gooney birds who would tip over until their beak went into a glass of water, then bob up straight until the water on their beak evaporated and the head started tipping down again."

Just a bit of chemistry here to explain what happens when you put stripper on a finish. The chemical molecule of methylene chloride is very tiny. So tiny that it sinks down through almost all finishes and quickly attacks the finish bond at the surface of the wood. This causes the finish to blister and fall off the surface.

However, since the molecule is so tiny, it easily passes through almost all other materials, from heavy rubber gloves, to protective clothes and skin. It quickly enters the blood and creates stress in most of the important organs, like the liver, heart and brain. My experience with it indicates that the body gradually becomes more sensitive to exposure, so that when I started using it, I had little reaction, but after a decade of use I would notice a strong reaction almost immediately upon opening the can. There are some reports of older people who experienced heart attacks while refinishing kitchen cabinets, for example, and did not connect the attack with the exposure to the chemical.

Certainly the most dramatic accident relating to furniture refinishers I know of occurred just a few blocks from my shop last year. A elderly woman hired some workers to refinish the wood trim in her historic craftsman home. These guys put flammable stripper on all the wood work in the house, without opening the doors or windows. Just as the woman was rushing out the back door to avoid the odor, the water heater kicked in and ignited the fumes, exploding the home and instantly destroying it. I saw the smoke and flames from my shop and rushed over to see what was happening. There were dozens of paint stripper cans in the front yard, and I tried to make a sick joke with the fireman who were fighting the fire, "I hope it wasn't the stripper!" I said. He just looked at me, and I knew.

If you must use methylene chloride, contact an industrial safety supply company, like Lab Safety. They will direct you to the proper gloves, suit, shoes, mask and breathing protection which will be necessary. For example, the chemical penetrates my old heavy rubber gloves in 6 minutes. The proper clothing can provide complete protection for many hours. Very important.

One problem with methylene chloride is that it completely removes all finish, color and patina. The color, stains and dyes are removed and you must start over to make it look "old". Not a good thing for fine antiques. I wanted to find another way to remove the finish, so I started to test other methods, which lead me to focus on denatured alcohol.

Denatured alcohol is a larger molecule than methylene chloride and can easily be used with minor protection. It is also a solvent for shellac and will dissolve other finishes given enough time. The problem is that it quickly evaporates, and I work in Southern California, where the climate is hot and dry most of the year.

I found a system which works wonderfully, is quick and easy and doesn't remove the patina from the wood. Since the wood grain is not raised, it doesn't require sanding, except in rare cases. I use paper towels, denatured alcohol, plastic food wrap and green scrubbing pads. I place the paper towels on the surface, add a lot of alcohol, cover the towels quickly with plastic wrap, smooth out the bubbles, and wait.

After 10 minutes or so, depending on the finish, I remove the covering and use more alcohol and scrubbing pads to wipe off the surface finish, leaving clean old wood. If required, I can repeat the process to remove stubborn finishes. Never use steel wool; only plastic pads. Steel wool can cause black spots, and scratch fine wood surfaces.

I have used this method to great success on evaporative finishes and those oil finishes made with alcohol soluble resins. Alcohol will not remove most cross linked finishes, such as chemical or UV cured urethanes, ureas, polyesters, and acrylics, nor will it remove most epoxy finishes, but all those finishes should never be applied to genuine antique surfaces.

I have used this method to get great results for many, many years, and I have no desire to open another can of methylene chloride ever again.

8 comments:

Alviti said...

What a well written post. I think we're all guilty of being a bit blazae with chemicals we use all the time. Like my "breath through my nose if its dusty".
Really we should all read up a bit more on what we're using and take note of the warnings on the tin.

W. Patrick Edwards said...

Unfortunately, all warning labels say the same thing: "Contains petroleum distillates...avoid direct contact...cannot be made non-poisonous..." etc.

These warning labels were created by industry attorneys, not chemists. They do not instruct the user as to specific dangers and precautions. They are too general to be useful.

Lately, the state of California has been requiring labels on practically every thing that say "the State of California has determined that this (thing) contains (stuff) which has been determined to cause cancer."

These kinds of warnings only serve to make the general public ignore actual dangers which exist.

They only serve to protect the industry from lawsuits when someone actually gets injured.

John Williams said...

Thank you for this post. I strip a lot of furniture, and am constantly getting "burned" by MC working thru my heavy nitrile gloves. I will definitely try the den. alcohol on the next project!

Anonymous said...

Thanks for this post and the alternate stripping method. And your comments about warning labels are spot on.
Jim B

Luke Townsley said...

I really appreciate this post. I'm giving the denatured alcohol a try.

Luke

W. Patrick Edwards said...

I am surprised at the number of comments this post has generated. I think that people are naturally concerned about chemical exposure in this business, and more can be done through blogs and internet searches to distribute helpful information which the chemical industry chooses not to make available to the general public.

One of the advantages of working with period finishes is that shellac, oils, waxes, protein glues and other materials from the pre industrial era are generally organic and not hazardous.

Joshua Klein said...

Thanks, Patrick for the helpful recommendations. I do, on occasion, use a paste remover with a high percentage of MC. I practically abhor those days of work. It is always my first goal to save and rejuvenate original (or existing) coatings so stripping isn't something I often do. I am told regular activated charcoal filters found on respirators are completely ineffective on MC. Have you heard this as well?
Great technique using alcohol. Certainly the plastic wrap is the key here due to its evaporation rate. I will have to give it a try. Have you experimented with gelling the solvent for vertical surfaces? If so, what do you use? Carbopol?
Thanks, Patrick. Great blog. I'll keep digging it's depths.
-Joshua Klein
Furniture Restorer
http://workbenchdiary.com

W. Patrick Edwards said...

It is true that any type of standard face respirator is not effective at protecting against methylene chloride. In a short amount of time the respirator will become saturated and allow the chemical to pass through.

I solved the problem years ago by spending a chunk of money on a system which uses an air pump, 75 feet of hose and a full face mask. This means I can put the pump in a safe area far away from the chemical, and that I can work very close to the chemical without any chance of exposure. Since the air pump provides a positive pressure of clean air into the face mask, there is no chance of outside air getting in.

I believe the cost at that time was about $1500 or so. I got the system from a local welding supply company. Be sure the air pump is designed to provide safe air for breathing.