OOPS!:doh:
Sorry I got carried away and completely forgot the bit about the pumice.
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I went to Carbatec today to buy pumice. They sold me U-Beaut Tripoli powder which they assured me was the same thing. After a bit of research I found it isn't pumice. It isn't rottenstone either. According to the U-Beaut website it is used AFTER French polishing to remove blemishes and impart a sheen.
So regardless of what it is, does anyone know if it is suitable as a grain filler for French polishing? If so, does it show up as white on dark timbers?
Tripoli Powder is definitely not Pumice Powder. It has been called rotten stone in Aus for a long time but it's not rotten stone/rottenstone either. It is Tripoli Stone. Mined in the US or the stuff we get is.Tripoli Powder is: A porous, friable, microcrystalline siliceous rock of sedimentary origin that is composed chiefly of chalcedony and microcrystalline quartz.
What we sell is called Air Float Cream (AFC) which is the finest grade and named so because if you throw some into the air it will hang there for quite some time.
Yes it can be used to fill the grain and as it basically goes in almost colourless it blends in well with most woods. However because it is so fine it may clog the pores of your rag.
Pumice doesn't really fill the grain with pumice although a portion iof it ends up in the pores. It fills the pores with the dust of the wood as the pumice is basically grinding the surface of the work like sandpaper and pressing the shellac sodden dust into the pores of the wood. So it's more a case of filling the wood with itself.
You can also use a very small amount of our Talc in some white shellac to fill the pores of very open grain wood. Maybe a teaspoon of talc to 250ml shellac. Brush on leave to dry well and sand with fine abrasive (no courser than 600 or 800 grit). The talc makes the sanding easy as it helps to not clog the abrasive. Works best with dewaxed shellac and can also be used with our sanding sealer. Don't do too many coats of it loses it's transparency and starts to become a bit translucent instead.