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Friction Polish and Paper Towels

John Roberts

John Roberts

Joined
Feb 28, 2019
Messages
15
Likes
6
Location
Henrico, VA
Hi Everyone! I encountered an issue I hadn't previously over the weekend with friction polish and paper towels. I've been using friction polish to finish small project/practice items. I started with Doctor's Woodshop High build Friction Polish (I believe Linseed/Shellac) with mixed results I think based on species. When it's great, it's great! But sometimes I'd get a cloudy portion of the wood that I can't seem to brighten up regardless of coats, sanding down/removing, etc. My gut tells me there's and issue with the wood like tearout, but I always do my due diligence with sanding 120 (80 if I have some real cleanup to do)-800 and if it's there, I can't see it. Being newer, I'm more than willing to accept user error, but any thoughts would be welcome. I've tried different mixtures of speed, pressure, applying with lathe on/off, applying a lot/little with each coat, and everything else I can think of, but it still seems to be harder than it should be so I must be doing something wrong. Everyone says with friction polish, speed is your friend, but does it ever get so high it turns into your enemy?

In any event, after looking around I decided to give Hut's Crystal Coat a try and have gotten much more consistent results. Only issue is as it's a bit thicker and stickier, I'm guessing due to the carnuba/shellac mixture, and it starts to saturate, and then pull apart the paper towel I use to apply it (before I notice), then integrating itself into the finish on the work piece. This obviously leading to removal and reapplication, which I'm sure most of you can relate to being a very frustrating process. As prevailing safety practice suggests, I don't use anything but paper towels to apply finish when the lathe is on, but after trying 3 different types of higher quality (kitchen) paper towels, I've decided to appeal to the wisdom of the forum. Would lower quality paper towels work better potentially? Shop paper towels? Cloth?

Appreciate everyone's advice as usual! Thanks!
 
Like Gary, I use small pieces (about 3 x 3 inches) of old t-shirts to apply finish. If doing it on the lathe, do NOT wrap the cloth around your fingers! Just use it as a small pad held in your fingers. If it decides to catch, it will be pulled away without taking a finger with it.
 
John, Just to be on the safe side...have you considered what species of wood the dull spots are on? I had a similar issue several years ago with an ornamental variety of soft maple. Take a look at where it pops up, and if it's across multiple bowls. If you see a pattern or some commonality, there's a chance it's the wood.

You might also rule out moisture in the wood, as that could be culprit, too. Of the oils I have used, walnut oil especially doesn't care for water in the wood. That might explain why the Doctor's shows more of an issue.

Good luck.
 
In the industrial world they use lint free rags, shop towels, paper towels that are a little tougher and more of a fabric design that does not break down like a cheap paper towels, the lint free feature is a plus when working with finishes.
 
Years ago on rec.crafts.woodturning, one of the early newsgroups on turning, before forums, I remember someone's advice about friction finishes. When applying do so lightly and in several applications. When using the application material, either quality paper towels ( I use Bounty) or as mentioned earlier a small piece of old cotton Tshirt, quickly alternate between the area of applicator surface with fresh polish and the area with no polish, so it can buff and generate the heat of friction to melt the shellac and at the same time transfer some additional polish. Some brush the finish on with the work stationary and then wipe gently with the applicator before high speed buffing. If you use too much liquid, you will see streaking build up. Clean it up with 0000 steel wool or synthetic equivalent and start again. I have used that advice ever since and it serves me well.
 
I've had good results with Bounty paper towels with the doctor's walnut oil/carnuba/shellac.
Keep in mind when using oil finishes with cotton that there is a possibility of spontaneous combustion if left wadded up.
Too much speed can be your enemy if you heat the wood enough to cause heat checks.
 
Zach LaPerriere said:
John, Just to be on the safe side...have you considered what species of wood the dull spots are on? I had a similar issue several years ago with an ornamental variety of soft maple. Take a look at where it pops up, and if it's across multiple bowls. If you see a pattern or some commonality, there's a chance it's the wood.

You might also rule out moisture in the wood, as that could be culprit, too. Of the oils I have used, walnut oil especially doesn't care for water in the wood. That might explain why the Doctor's shows more of an issue.

Good luck.
Click to expand...
Thanks Zach! I've seen it on Black Walnut, and some mystery hardwoods I've gotten from the B bin at woodcraft. Think they could be some kind of rosewood, but I'm not certain. As for moisture, they're normally running 15-16% before going on the lathe so probably a little drier.
 
John Roberts said:
Thanks Zach! I've seen it on Black Walnut, and some mystery hardwoods I've gotten from the B bin at woodcraft. Think they could be some kind of rosewood, but I'm not certain. As for moisture, they're normally running 15-16% before going on the lathe so probably a little drier.
Click to expand...

No problem John. That's pretty high moisture for a finished bowl...below 10% is pretty standard. I wouldn't be surprised if that may be some of the issue with walnut oil. If you intend to let the bowl warp, you might just leave the tenon on, let it dry further, then put the oil on. Or, you could use an oil that is more tolerant of water, such as Danish or tung oil.

Keep having fun!
 
John,
I strongly recommend you try applying your friction polish to the wood with the lathe OFF. (You can rotate by hand.) This allows you to get a complete and uniform application. Then to polish it with heat, turn on the lathe and apply fresh paper with a little pressure.

Also, I was advised early on that friction polish shouldn't be applied heavily. Just a few drops will cover a small piece with a thin layer. This may not be the practice of everyone, but it seems to work for me. Sometimes I'll do the same thing a second time, if I haven't gotten the result I want, but I honestly can't say it's generally improved the original single coat finish.
 
I understand all Doctor's Woodshop finishes are walnut oil based utilizing NO solvents. I agree and follow the above listed protocols for oil-finish rags to prevent spontaneous combustion; but with no VOCs present, I'm unsure what could be the cause of combustion?
 
Max, the spontaneous combustion that can occur with drying oils (and products that contain them) has nothing to do with any of the solvents. In fact, the solvents evaporate relatively quickly.

The problem is the oils themselves. These oils "dry" through a process called oxidation which generates heat. When the oils are in a bulk container, little oxygen is present and very little if any oxidation occurs. However when applied in a thin layer on a project, oxidation occurs more quickly as the ratio of oxygen to oil surface area increases. This process does generate heat, but is not noticeable because the large surface area quickly dissipates that heat.

When you take a rag or towel that is saturated with oil and wad it up or throw it in a pile, the ratio of oil to surface area is large and the heat generated may not dissipate and could result in combustion when critical temperatures are reached.
 
Max Monts said:
I understand all Doctor's Woodshop finishes are walnut oil based utilizing NO solvents. I agree and follow the above listed protocols for oil-finish rags to prevent spontaneous combustion; but with no VOCs present, I'm unsure what could be the cause of combustion?
Click to expand...

It's not the VOC's that are the problem because they flash off rather quickly. The problem is that the crosslinking curing process of the oil is a highly exothermic chemical reaction. The process occurs slowly in walnut oil (assuming that it really is pure walnut oil) so I wouldn't expect it to be a significant problem, but linseed oil and tung oil that have metallic salt dryers added to accelerate curing definitely are a concern. Several years ago I did an experiment to see if this really is as much a problem as claimed and found out that it really is. I stuffed a bunch of rags and paper towels that had been soaked with linseed oil into an empty can and then set it out in the vegetable garden. I checked on it several times and it got extremely hot after several hours. The next day I emptied the contents and everything was charred black. So, under the right conditions spontaneous combustion really can occur.
 
Yep, those metallic dryers seem to be related to the exothermic reaction. The info on the Doctor's Woodshop site is that the oil is treated and filtered to remove the allergens. I did grab this from the MSDS sheet on the Walnut oil: (sorry for the all caps, but it's quoted from the site)
*UNUSUAL FIRE AND EXPLOSION HAZARDS* NONE. MATERIAL IS NOT PYROPHORIC, DOES NOT REACT WITH WATER, NOT AN OXYGEN DONOR, MATERIAL IS SHOCK STABLE
Also, *HAZARDOUS COMBUSTIBLE OF DECOMPOSITION PRODUCTS*
So, not pyrophoric nor an O2 donor. BUT, the sheet DOES caution to use closed metal containers for disposal, so safety first, fer sure!
I like to learn a new word and today's is " pyrophoric". I already knew exothermic...Thanks for the chat, Tim & Bill!
 
And, I learned "pyrophoric". I suppose that I ought to look it up to see what it means before bandying it around. :)

EDIT: Looked it up and borderline obvious. "pyro" from Greek pur -- fire + "phoric" from Greek phoros -- to bear = "fire bearing" or spontaneous combustion in today's English.
 
I have sanded to different grits for different woods after having some issues with a dull finish. Maybe it's just coincidence, but on some woods I have a hard time with friction polish and/or CA sticking when sanded that smooth. I almost always call it good at 400. If there are visible scratches at 400, I backtrack grits.

Also, if the wood has soft or punky spots, I buff in linseed or walnut oil at a few hundred rpm unt I can get a uniform sheen. That seems to give a more even foundation for all three finishes I use.
 
Thanks everyone for the direction and vocabulary lesson! I'm sure it will keep me from self imposed defenestration at some point (look that one up :)).
 
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