The debate among Ellijay log home restoration contractors rages on as to the proper way to remove old finishes from a log surface. Use a chemical and blast it off with water pressure, or use crushed corn cob and blast it off with compressed air. Those are the choices.
The contractor that prefers Ellijay chemicals and a pressure washer will tell you that cob blasting will pit the wood, create much unwanted dust inside and outside the home and cost twice as much as chemical stripping.
The contractor that prefers Ellijay cob blasting will tell you the chemical and pressure washing process will make the wood “fuzzy” and the pressure of the water will shoot through the walls and get inside the house causing water damage and mildew problems. Both are legitimate concerns and although both statements are true to some degree, to the homeowner neither chemical nor cob blasting sounds like a viable option.
However, when properly executed, both have their place and are very effective methods for removing different types of finishes. When improperly used, both can cause extensive damage not only to the logs, but also to metal trim, glass, vinyl as well as causing damage to the inside of your log home from excessive dust and or water. Needless to say, only the most experienced professional should be allowed to use either method on your log home.
Most log homes today still have oil based stains and sealers on them. In this case chemical stripping is the preferred method of removing these coatings.
There are however exceptions. Some of the harder “film forming” stains including linseed oil based stains and latex stains and paints may not respond well to chemical stripping and will have to be removed by cob blasting. These are usually few and far between, however as latex stains grow in popularity so will cob blasting.
With chemical stripping, it is all about the process, not the pressure! The chemical is the tool that does the work, not the pressure washer. The pressure washer we use is more for the volume of water (six gallons per minute) rather than the pressure. We start by mixing a weak solution of stripper and apply it to the logs by spray. It is allowed to “dwell” for a predetermined length of time. At this point we do a test spot to see how the sealer responds to the stripper. If needed, we will adjust the solution to an optimal strength to remove the sealer in an efficient manner but in such a way as to minimize “furring” to the wood. Depending on the sealer, some “furring” of the wood is to be expected. This is easily removed using defelting pads later in the process.
While chemical stripping, my wife is on the inside of the log home checking for leaks. And there will be leaks. We have never restored a log home yet that did not leak to some degree. Even the most expensive log homes leak….It’s still a log! Leaks are not necessarily bad. The water is really a good indicator to pinpoint where the home does have leaks. As the leaks are found, we will tag the spot where the leak occurred so that we can come back later and address the issue by caulking, weather stripping, chinking or whatever means is necessary to remedy the leak making the house weather tight.
Once the stripping is completed, it must be neutralized and allowed sufficient time to dry before sealing. This usually takes two to four days, but the only way to know for sure is to test with a moisture meter. An 18% moisture content or lower is required before any type of finish is applied.
This method of removing old finishes is safe and reliable if used properly. However, to the inexperienced, too strong of a chemical mix and you can not only “fur” the wood, but it can actually soften the wood to the point it must be replaced. Too much pressure and you can not only “fur” the wood, but you can gouge out the wood, as well as cause damage to other areas of the home such as siding and windows. Be sure you have someone that knows what they are doing and chemical stripping is a viable solution to removing old finishes.
With Cob Blasting, really the same thing holds true. It’s the process. The name itself scares some people because they are not familiar with this process. Blasting consist of using compressed air and a lot of it (at least 185cfms) and mixing it with some type of media, in this case ground up or crushed corn cob. The mix is then blown out of a nozzle toward the log surface where it impacts at great force, knocking off the old finish. Corn cob is used because it is relatively soft and will not damage the underlying wood (if you know how to use it.)
One of the biggest problems with cob blasting is the copious amounts of dust. The average house may use as much as a ton or more of corn cob media. That is a lot of media blowing around, and it will get in every, and I mean every nook, cranny, crevasse, and corner there is inside and out of the home. We cover all the flat surfaces and furniture as well as put plastic up around the perimeter of the inside of the home to help confine the dust to the walls and not out into the rooms, but some still manages to get by.
The other problem with cob blasting is it takes off a layer of wood and leaves a profile in the wood. Depending on how good the operator is will determine how much wood and how deep the profile will be. This is a harsh process but like the advantage of chemical stripping locates leaks, the profile left by the blasting creates a good “tooth” and porous surface to accept the new stain.
Chemical stripping and cob blasting both have advantages and disadvantages. Used in the right situation by an experienced operator, they both have a place in the log home restoration process. To put one above the other would be limiting the means by which to be able to remove a particular coating from the log surface. So after an assessment has been made of the existing finish to determine it’s type, then an educated decision can be made as to the best method to use to remove the finish. When the facts are known about cob blasting and chemical stripping, there really should be no debate. So, I hereby declare the chemical strip vs. cob blasting debate resolved.