Dent Repair Debate
Pros compare steam treatment to sanding and refinishing for repair of a compression mark in a finished cherry piece. March 29, 2006
Question
Does anyone have suggestions on how to repair compression mark in tung oil and wax finish on solid cherry?
Forum Responses
(Finishing Forum)
From contributor A:
Try some mineral spirits to take off the wax, and then a hot iron with a damp cloth.
Take off fuzz with 400 grit and reapply tung and wax.
From contributor B:
Removing the wax is excellent advice, but the problem will be the tung oil finish under the wax that maybe affected by the heat of the iron. He only mentioned a compression mark, but if the compression is only in the coating, he may be better off sanding down the coating and then building it back up with more oil finish, sanding in between coats. If the compression is down into the substrate, that is a bigger problem. In that case, he may be able to sand it out, but if not, he will have to fill in the compression and then sand it level - and then begin to build the oil finish back up.
From contributor C:
I would use sanding as a last resort unless you just finished the piece as cherry will darken considerably in 2 weeks to a month depending on the light it is exposed to. Any sanding you do will expose the unoxidized wood, which will be very noticeable.
From contributor B:
The technique of using an iron with steam to raise the dents is intended to be used on raw wood, not on woods that have been coated. It causes more problems than it fixes.
From contributor A:
I've had success in raising finished dents by pricking needle holes through the finish in the bottom of the dent, filling it with a few drops of water and then heating with my pencil soldering iron. Then I sand a bit with 400 and touch it up with a shot of Mohawk lacquer.
From the original questioner:
I like the idea of piercing finish. The oil layer is fairly thick and I was leaning towards a clear or amber filler that would adhere to the oil. Has anybody tried thickening tung oil?
From contributor B:
You never did mention how deep the compression mark is - is it only in the coating, or is it down into the wood? You are talking about two different repairs. You might be better off just filling, sanding and recoating.
I would like to add this to the post so others who may read it can consider the idea of trying to raise the coated dent with steam, or trying to pierce the coating with a needle. This is my opinion, others may differ. Think twice, finish once.....
Steaming on a film coating is not an option that I would try, because either it will not work in most cases, or it can damage the wood and the coating. If you try pricking pinholes in the coating, and then drop in some water, and then try steaming it, the chances are greater that you will discolor the wood from the steam. You also will weaken the bond between the wood and the coating, and there is a chance that you will get lifting in the coating. You also will still have to repair the pinholes that are down into the wood and the coating.
From contributor A:
Of course you are going to have to finish the repair by renewing the coating and whatever else is required. That would be after the dent is raised.
From contributor B:
I think it would be better to just burn it in level, then sand, and then the oiling, rather then going the pricking holes and steaming route.
From contributor D:
Steam will penetrate all but the most extreme of waterproof finishes. Steam will penetrate many films that water will not. There is no need to prick finishes - the steam will go right through them. I have done many repairs by steaming a damp rag with an iron or heat gun. It is my common experience that these methods are only partially successful - the dents will partially swell back into shape but still leave a smaller depression. Sometimes they will be completely successful though and I rate the risks as quite low so I usually try them first. In addition, a partial lift allows for a shallower fill which speeds the repair process. Scorching, melting finish, sheen changes, are the major risks involved in the steaming process. I minimize them by using a careful approach, a digitally controlled heat gun temperature, water spray gun handy, and progressive application of heat. Softwoods dent easier than hardwoods but usually swell back easier too. Commonly the local area requires re-sheening and/or touch ups and/or surface filling in addition to the steam treatment, but I rarely bypass this important step. I can only say that it really works for me and for those of you who haven't used it much, I would suggest taking another look because it may make your life easier.
From contributor E:
Once a wood has a film build of finish, one should consider the following:
1. Determine first how deep the defect is. Think about the plan of action before you quickly grab sandpaper or sweating tools.
2. If the defect is shallow enough and can be abraded or wet sanded out without creating a dip, this would be an easy way out.
3. If the defect is deeper or larger and requires a fill, then either fill it with a burn in process or brush thin layers of finish to the area until it becomes flush enough to the surrounding surfaces to allow a rubbing and sheen blending process to take place. When brushing finish into defects, apply thin layers and ample dry time between applications to prevent shrinkage.
I don't feel comfortable sweating out dents on film building finishes either. I prefer to fill them, add color and grain to them if necessary and I always expect to have to blend the gloss with some kind of rubbing procedure at the end. For me that's the fastest way. The repair area doesn't usually grow or spread and I get decent results for acceptable repairs.
Recourse on finish repairs depends mostly on the individual repair person’s strengths. People who are timid of the burn in knife will migrate to what they are comfortable with, and rightfully so. Spot repairs on wood finishes can be difficult to do. Take the plan of action that you feel most comfortable performing and hopefully end up with acceptable results. Practice, practice, practice - if you have any spare time. Spot repair people are in demand and it's a profitable trade.
