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Im currently in the process of filling IRW back and sides of a classical. Ive wisely decided to do a test FP on some Opp grade Allied IRW. Im following the Milton brothers FP guide from this forum.

I wiped on 4 spit coats of 2 lb cut shellac waiting at least 30 minutes between coats and left last coat over night before starting work with pumice.

Ive followed Milton's instructions re applying pumice and Im using Behlens 4F pumice. They emphasise that NO extra shellac should be applied during the pumicing process...only alcohol.

As I apply the pumice Im having major problems with the stuff caking up into hard deposits.

I notice that alot of other people use a lubricant with their pumice to prevent this....either 10% shellac or oil. One reference discusses coating the wood with oil before applying pumice.

Any assistance from the FP Gurus would be much appreciated.

TIA

kiwigeo38964.8777893518

Okay after searching through the archives Ive come to the conclusion that my problem is either 1. Too much pumice on the pad and/or 2. too much shellac on the spit coats.

Im using 4F pumice and making sure I clear the pumice from the pad before working the wood surface.

Im using 2lb cut shellac on the spit coats. I went to 4 coats as after 3 coats the coevareg didnt look good. Maybe that was one mistake I made. Should I go to a lighter cut?

During working there wasnt alot of evidence of any sanding action going on. The muneca was wearing out slowly but I would have expected higher rate of wear of same, especially if I was overloading the muneca.

Martin,

There are other better fp experts out there that will chime in. I only pumiced filled once and it is a very tricky and laborious technique. When I got hard deposits of pumice I loaded more alchohol on the municea and worked away at them to disperse them around. If they are two big to shift you may have to scrape them off. You can definitely hear and feel the grinding as you go. Just work in small areas and don't overdo the pumice.

I liked the results but would now probably use Z-poxy to fill and FP over that.

Good luck.

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

I used Zpoxy and am curious also as to your pumice question. Hopefully, Michael P. will chime in on this one.

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

Thanks Dave,

Spiriting off the excess pumice would seem to be the solution going from previous posts on the subject. Ive left the failed grain filling attempt as is and started again on the other side of the piece of rosewood. On the second attempt Ill use 3 spit coats (2lb cut) and try to use alot less pumice.

Grain filling using pumice isnt supposed to be easy so the failed first attempt comes as no surprise.

Cheers

Yes, Michael undoubtedly the expert on FP. I could have gone for the epoxy option but Im old fashioned and stubborn so am determined to master the old fashioned techniques as well as the modern ones.

Well here again the really hardest part of the the Milburn process is pumice filling. My assumption is three fold, one there is too much shellac on the body for the fill process and two, there was too much pumice on the muneca. Three two pound spit coats sounds heavy.

With out a doubt pumice filling is the most difficult part of the process

The idea behind pumice filling is for the the pumice to drag off fibers of the wood and deposit them in the pores. Many people think the pumice is the filling agent but this is not true. It is part of the slurry that gets trapped in the pores but not nearly the majority. The pumice is an abrasive. So if there is too much shellac on the surface all it can abrase is the shellac and ends up causing a big glob of shellac and pumice.

It is also important not to use too much pumice and to clear it completely on the muneca before attempting the fill. Less is better than more.

If you re-read the Milburn tutorial I believe you will find that they used a 1# spit coat and 2# to seal purflings and the top from the pumice dragging back and side wood oils and color stains.

The best way to clear the mess is to scrape back to bare wood a start again. or to scrape off the gum balls and spirit-off til you have a thin level surface. If there is still too much shellac then the pumice fill will ball up again.

I will re-read the Milburn tutorial tonight and see if they really call for 3, 2# cut spit coats. That seems very heavy to me. A couple drops of oil will not hurt but should not be needed.

It is also possible that you inner pad still has too much shellac if 2# cut was applied heavy.
MichaelP38965.4173842593

Thanks for the words of wisdom Michael, Looks like I need to re-read the Milton tutorial as well. I was pretty sure they stipulate application of 3 x 2lb cut spit coats before starting the pumicing.

Cheers

Martin,
You keep stating the Milton tutorial I believe you are actually referring to the Milburn tutorial. but there may be a Milton tutorial as well that I am not acquainted with.MichaelP38965.4464814815

Pumice filling is the most fool-proof method I have found for filling. The color match is always perfect, something not achieved with paste wood fillers, which are either too light or too dark. Epoxy filling is not something I am drawn to due to the toxic nature and uncertain results as the epoxy gasses off excess hardener. Pumice filling never really clicked for me until I read in Fine Woodworking about a guy who fills with pumice and wiping varnish on his furmiture. He just kept wiping on pumice and varnish until the pores were full and the top of the wood was just sealed. Pumice is essentially glass, so it becomes clear when made into an emulsion with a binder like shellac. What you are shooting for as the end result of pumice filling is to have the pores packed with the shellac/pumice mixture and the wood surface just barely sealed. Coarser pumice is better than finer as it take up more space and it doesn't shrink into the pores as much as finer grades. I start with a rag soaked with shellac, sprinkle a good bit of coarse pumice on the surface and work the pumice into the pores. It dries very quickly. Then I come over it with a rag that has just alcohol that picks up the excess pumice on the surface and works it into the pores as well. As the alcohol pad dries out it becomes glazed with pumice and shellac. This is when you can do the most effective filling, moving the pad with the grain. If you keep in mind that the idea is to not have any shellac on the surface when you are done, it may click for you as well. Very light purflings of porous wood might pick up dye from the other woods, so this method might not be a good choice for this. If your purflings are hard maple or the like, it should present no problems as you can always wipe the dye off with a fresh alcohol-soaked rag.

_________________
Stay with the happy people.
--Reynolds Large

Wow!!! that goes against nearly 35 years of pumice filling on FP finishes I have done, mostly on cabinets and tables. It is true that the pumice will be part of your slurry but its main job is to pull micro fibers from the wood that will make up the majority of the slurry. At least this is what I have been taught, and what I strive for. I am not discounting what you have posted just look at your post from a experienced French polishers view point. I also disagree in the course pumice. FFFF is what use and would not use courser.

Michael,
You are no doubt more versed in proper FP technique than I am. All I know is my method is working very well. Lots of Brazilian builders use finely ground coffee and shellac to make a slurry and fill the pores. It is the same concept: an inert filler as a bulking agent and a binder to hold it in place. A paste wood filler consists of a coarse, mineral bulking agent, a binder (whether acrylic for waterbase or oil varnish for oil base), and a pigment. My method dispenses with dissimilar materials, like oil varnish binder and shellac topcoat, and also does away with pigments. The tenacious bond of shellac holds the pumice in place. The pumice becomes as clear as glass and the amount of coloring you pick up from the wood tints the shellac to exactly the perfect color.
As an aside, there are some elements of furniture FP technique that do not transpose very well to instruments- the use of linseed oil comes to mind. Linseed oil is specified in just about all the old texts on polishing. It did not work for me, the difference possibly being a guitar is held against your chest and perspired upon, while a piece of furniture just has to look nice and withstand the occasional dusting. I have had to strip more than one linseed oil polished guitar when the film turned white at the points of contact with the player's body. Bad technique? Probably. But I have had no problems like this since switching to walnut oil, and I do use a fair amount of oil in the process.

_________________
Stay with the happy people.
--Reynolds Large

Milburn not Milton...yes youre right Michael. My apologies to Orville and Bob.

[QUOTE=TRein] Michael,
Lots of Brazilian builders use finely ground coffee and shellac to make a slurry and fill the pores. It is the same concept: an inert filler as a bulking agent and a binder to hold it in place. [/QUOTE]

...or they use end grain sawdust and shellac. This is a perfect color match evertime and very easy to do. It is my favorite pore filling method.

Okay I think Im making a bit of progress. I sanded and scraped back my first (failed) attempt at pumicing and started again. I put on two spit coats of 1.5 lb shellac and then pumiced again this time using alot less pumice and making sure muneca was clear of pumice before applying to the surface. No gunk build up this time and a noticeable reduction in pore cavities on the wood surface. Its not completely smooth though.

Can I do a second pumice application? Should I apply another spit coat before same or rely on shellac still left on surface and in pores?

TIAkiwigeo38966.4006481481

Yes you fill till you are happy with the surface. In most porous woods one session seldom completes the fill.

You can also go back and pumice fill spots you missed even after you start your bodying sessions. FP is cool stuff.

_________________
Horton, MI

Thanks for the input guys....a great help.

Michael I had a re-read of Milburns tutorial and Im pretty sure they say to put on 3 spit coats prior to pumicing. No actual stipulation on cout of same but the previous chapter in the tutorial talks about only 2lb cut so I assumed that was what they use on spit coat. Anyway Ive only used two coats of 1.4lb shellac and cut down on pumice so either one or both measures seem to have worked.

Cheers

Some progress pics of the French Polish job in progress. I ended up doing 4 pumicing sessions. Had to apply another spit coat after 3rd session. I would have gone for a 5th session but colour was starting to leach out of the IRW.

Pics show guitar after on bodying session. Still following Milburn brothers tutorial. Man I just loooooove that little plume that trails behind the muneca!!

Martin,

That is looking quite good! It seems as though it will definitely be worth the effort you've had to put into it.

Thanks for the positive reinforcement Carlton!

Onto the 3rd bodying session.....a few little blemishes here and there but managed to work them out with 1200 wet and dry lubed with olive oil. Still not 100% happy with the pumice fill job but hopefully after a few more body sessions things will look better. kiwigeo38971.2446527778

Looks like the FP is coming along nicely, great looking classical.

Thanks Marc, its a fairly vanilla flavoured instrument based on a Torres design. Only major boo boo was a bit of a gap between heel and body...angle of side slots in heel block werent quite right angle.