Pumice and Rottenstone as wood filler.
When you go through the catalogs and look at all of the finished that are available, you will not see this tip.
They sell you Pumice and Rottenstone to be used as a buffing and polishing agent to bring up a gloss on the surface, but no one tells you about using it as wood filler. The interesting thing about Pumice is it is basically transparent so if you use it as wood filler it doesn’t contribute any different colors to the wood that it’s being used on. The Mfg version of Oak wood filler might not be the same shade that your board is, so what happens is you fill the pores of you wood with a different color wood. Maybe this is what you want, maybe it isn’t. The Rottenstone on the other hand is black wood filler. It is great for use on Walnut and other dark porous woods. It makes the grain lines visible. Remember you don’t use wood filler on cherry or maple because the pores of the wood are not present. Where red Oak and walnut have a porous surface. If you want a smooth gloss surface you want to fill all of the pores.
I took a finishing class taught by Jeff Jewitt and this was one of the tips that he gave us in the class.
Here are the materials that you use.
I use a salt and pepper shaker to store the working Pumice and Rottenstone. Just don’t put them on the picnic table or get them to your kitchen. It could mess up a bunch of food. I believe that they make a FFFF version of Pumice. The number of F’s equate to the fineness of the grit in the polishing compound. It doesn’t make any difference which one you use. I use Butchers paper as a work surface because it has a plastic surface on the paper.
The tools are:
I use the metal putty knife to mix the Boiled Linseed Oil (BLO) and the Pumice or Rottenstone. I mix it on the board that I’m going to use it on. I use a rubber spreader that I bought at a Professional Automotive Finish store. It’s used to spread body putty in damage of cars. I’ve also used a small window squeegee and I’ve used the putty knife. I stuck a small piece of Formica because it could also possibility be used.
I used BLO for this demo but I might also try Danish Oil because it dried harder than just BLO. A homemade version of Danish Oil is 1/3 or each Mineral Spirits, BLO (Deft says that they use Teak Oil) and Varnish.
Dump some oil on the board and then dump some rottenstone on top of it. 
Mix it up and make it thick. Remember though that the oil soaks into the wood so it will continue to get thicker as you use it.
Spread it over the board and force it into the pores of the wood. I’m now using the rubber spreader.
Note I’m using a sample of Red Oak and Walnut. When you drag the slurry you want to pull it across the grain. You don’t want to go with the grain because you might pull the slurry out of the pores.
It will slip over the edges, but if you are doing a piece of furniture, you might only want to do this on the top because that’s where the pores would be most visible. 
You will also note that the rottenstone also darkened up the sapwood of the walnut piece. Use masking tape and paper to keep it from where you don’t want it.
The next sample will be using Pumice.
Pour your oil.
Then mix in the pumice.
Force it into the pores. NOTE: I’m not using the rubber block on the pumice because the abrading effect of the pumice could actually cut some of the black rubber into the slurry. I didn’t want that.
Do the final pass to force the slurry into the pores and clear off all extra.
All done with the pumice demo pieces.
Now the control pieces. Just the BLO and no filler materials.
Now finished these pieces.
These are the three sets of the boards. I’ll let them sit for a couple of days so that the finish will harden some. It’s this time where the Danish Oil would be faster. The Rottenstone is on the left. The Pumice is in the middle and the control piece with only BLO is on the right. These boards are after 12 sitting but still not wiped off.
I’ll continue this in another blog in a couple of days.
-- Karson Southern Delaware karson_morrison@bigfoot.com
14 comments so far
Roger Strautman
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496 posts in 614 days
posted 470 days ago
Thanks Karson! I learned something new today. Now can I go to the house for supper? LOL!
-- " All Things At First Appear Difficult"
Karson
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posted 470 days ago
Rog: Glad to contribute to your base of knowledge. And, also allow you to go eat.
-- Karson Southern Delaware karson_morrison@bigfoot.com
MsDebbieP
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11909 posts in 641 days
posted 470 days ago
isn’t that interesting!!!
“across the grain”.. makes sense!
-- "Functional WoodArt" by Debbie, Canada (http://www.execulink.com/~yohan)
FMOmbr
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47 posts in 565 days
posted 470 days ago
My wife wants to know when you took Jeff Jewitt’s class; she took a class with Jeff on finishing @ Marc Adams School and uses this technique on mahogany with much success. You have been generous with your knowledge. Thanks.
Karson
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12889 posts in 881 days
posted 470 days ago
I took this class
Hand Applied Finishes
By Jeff Jewitt 6/22/2002
At Thaddeus Stevens College of Technology
The host of the class was Steve Latta who was the administrator of the woodworking program at the university. Steve is quite well known for his Federal Period woodworking, and writes a lot of articles in woodworking magazines.
-- Karson Southern Delaware karson_morrison@bigfoot.com
Sawdust2
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847 posts in 568 days
posted 470 days ago
Thanks, Karson.
I’ve been using pumice and rottenstone for years and never saw this as an option.
You can teach an old dog new tricks!
-- No piece is cut too short. It was meant for a smaller project.
oscorner
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4576 posts in 791 days
posted 470 days ago
I prefer the pumice application because it doesn’t affect the original look of the wood grain. Of course, I am sure there are times that the rottenstone effect of the grain would be desireable. Karson, you are doing a wonderful job of sharing this information. I never knew about using either of these for a wood filler. I usually use wood glue and sawdust to patch and avoid wood fillers because of the fact that it is almost impossible to match the wood to the filler.
-- Jesus is Lord!
TheGravedigger
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196 posts in 505 days
posted 470 days ago
Sweet technique! I especially like the way rottenstone brings out the grain in oak. This would be really interesting after fuming white oak in the Mission style. Hmm…something to play with.
-- Robert from Raymond, MS. "We are what we repeatedly do. Excellence is therefore not a practice, but a habit." - Aristotle
furnitologist
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169 posts in 493 days
posted 470 days ago
Hey Karson….....SWEET…......Danish Oil and the Pumice…...super tip…...never knew that…....THANKS!!!!
Neil
cheller
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228 posts in 590 days
posted 470 days ago
I just tried a similar method, from an article in FWW (I think I’ll have to look). The method in the article had you sprinkle the pumice on the wood then rub in with a rag soaked in boiled linseed oil. While working on it I decided it would be much easier to mix the two first and apply with a putty knife – which is of course exactly what you showed here. I do like the look of the piece so far. I’ve got a second piece (foot stool) to do and I think I’ll try your method. Results will be posted later.
Incidentally the article also suggested plaster of paris as an alternative wood filler which would, of course, lighten the grain. It was suggested mostly as a quicker alternative.
-- Chelle http://artsgranddaughter.blogspot.com
Karson
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posted 470 days ago
Cheller: I’ve done something similar to what you suggested but it was done while veneering. In that case you used Shellac and sprinkled the pumice on the French Polishing pad and you rubbed the surface. It then placed a combination of wood dust and pumice into the pores of the veneer along with the shellac. It is used as a surface filler as you do the French Polish.
The boards that I pictured above were placed outside today in the sun. The oak board with just the BLO started to weep a little oil to the surface as the board heated up. The Pumice Oak board had a couple of spots and the Rottenstone version had none. That might also be a case where the Pumice and Rottenstone soaked up any excess BLO. Or, it’s a case where the slurry was thick and not as much BLO soaked into the surface anyway.
The walnut boards had no oozing at all on any of the boards.
The pores on the two boards that had the filler are completely full while the BLO versions still have open pores.
I was (and may still today) make my own Danish Oil and try the pumice and rottonstone again on the oak. I got lots of pieces like the ones shown. They were from the toy club and I was going to make 800 wheels with the boards. I can still use them for that because I only put the hole saw part of the way through and then use a resaw to free them up.
-- Karson Southern Delaware karson_morrison@bigfoot.com
cheller
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posted 469 days ago
I took a look last night and the article I mentioned was by Jeff Jewitt from FWW May/June 2005.
-- Chelle http://artsgranddaughter.blogspot.com
Karson
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posted 469 days ago
Yes same instructor, for the class I took. Jeff also has some books on finishing. Here is his website
-- Karson Southern Delaware karson_morrison@bigfoot.com
Zuki
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851 posts in 558 days
posted 461 days ago
Interesting. I just finished watching the Wood Whisperer who did some grain filling as well. He showed two approached . . . one using oil and the other using a commercial grain filler.
-- The significant problems we face cannot be solved by the same level of thinking that created them