tkvancil
fully equipped rock polisher
Member since September 2011
Posts: 1,547
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Post by tkvancil on Nov 10, 2018 14:36:06 GMT -5
Great for a first batch p40whk !!! I'm with the others who singled out that Bahia, it's really cool. As to removing flaws, what has been said already is spot on. I always say ... "If you don't like it coming out of coarse grind your probably not going to like it polished. As for the Sodalite not shining as well as the others .... It is one of "those rocks". One of those stones that by it's make up is difficult to get a good shine on. In the case of Sodalite it has 6 planes of cleavage with loose bonding between layers. We see these as tiny cracks when they are tumbled smooth. These cracks break up the surface giving the appearance of a lesser shine. Looked at under magnification the spaces between cracks are probably just as shiny as your other rocks. One thing I do to lessen this is to use a finer grit for the fist stage. I have observed that coarser grits dig in to these cracks more aggressively than finer grits. I start many rocks in 220 grit, Sodalite, most feldspars and sometimes obsidian. The 220 will shape and round but will take more cleanouts to get desired shape. These were done starting with 220 and took about twice as long to rough out. Which for me meant 8 to 10 weeks as opposed to 3 to 5 weeks with coarse grit. IMG_3494 by Ken Vancil, on Flickr Not perfect but pretty good.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Nov 11, 2018 4:14:24 GMT -5
Guessing someone has mentioned this detail. If you start with perfectly flawless material you will end up with similar tumbles. Many here will not only get flawless material but will also pre-shape it on a grinder to remove concavities and hard-to-tumble divots, etc. excellent work: Example of pre-shaped tumbles of flawless material. Pretty much gaurenteed perfect tumbles: Some from above batch finished, poor photo but telling enough
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p40whk
starting to shine!
Member since October 2018
Posts: 45
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Post by p40whk on Nov 11, 2018 19:59:35 GMT -5
Thanks Ken and James for the great advice. I am actually starting to look into what I need to preshape some of my rock and I am taking a closer look at what goes into the rough stage.
I just pulled a batch of Bahai agate out of the rough stage after 2 weeks and still am not happy with it so I charged the drum and they're off an rolling for another week. I do think I may have had too much water in the drum as the slurry was very runny which may have kept the rocks from getting as smooth as I would have liked.
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jamesp
Cave Dweller
Member since October 2012
Posts: 36,563
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Post by jamesp on Nov 12, 2018 1:13:53 GMT -5
A cheap tile saw can do some fine preshape
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