puipeb
off to a rocking start
Member since April 2020
Posts: 2
|
Post by puipeb on Jun 14, 2020 11:07:05 GMT -5
I recently ran a great batch of large chevron amethyst through to polish in a Lortone QT6. After burnishing, I noticed some of the stones were beautifully polished on the flat surfaces but, very rough (bruised?) on the edges. Some stones also showed surface spots like they had been hit with a microscopic hammer. Being an idiot, I did not closely inspect the stones after each grit stage/grind so, I don't know when the damages occurred. I used the same amount if mixed ceramic media {25%?) at recommended amounts after the rough stage.
This edge bruising also ruined large batches of Tiger Eye, Clear Quartz an Girasol. The only stones that seem immune are cherts, agates and jaspers - (the really tough stones).
Now, I know what you may say. "Add more media!" The problem is, I can't find someone that gives detailed information on amounts of media loading, level of tumbler loads and level of water filling. I have done batches heavily loaded with media, only to find that they take enormous amounts of time to go from rough to polish (3 to 5 months).
I am meticulous with cleaning between grinds, and removing stones that can chip and cause problems. This isn't my first rodeo but, I feel like a noobie all over again.
Currently, I separated out the damaged stones, added mixed ceramic media up to 3/4 full (makes about 60% media), added water up to nearly the top of the media and started the batch back at 60/90F SiC.
This is heartbreaking because, the stones are of incredible quality and beautifully polished on the flat surfaces.
Is there anyone out there who experienced this problem as they progressed from beginner to experienced tumbler? If you solved the problem, how did you do it? Please be specific.
A vibratory tumbler is out of the question because of noise.
I really need this forums help!
|
|
pizzano
Cave Dweller
Member since February 2018
Posts: 1,390
|
Post by pizzano on Jun 14, 2020 12:01:28 GMT -5
So, it's not your first rodeo........then you have experience with the QT6 rotary. But how much experience with Amethyst.......?
Banded Amethyst, "chevron" as you call it, or any Amethyst that has been "crushed" processed as rough tumble material, is tricky do get a really even and well sculptured polish due to the common internal fractures that will get exposed during the various stages of grinding. Banging around in a rotary, regardless of the type of filler (ceramics) being used, does not help. Since you've probably made sure that everything in that batch was of like hardness and similar texture, that is not the problem, But when I've rotary tumbled this material, I've made sure nothing but Amethyst and ceramics were mixed together. That helped, and yes it took weeks to get nice rounded results.........being a 7mohs material.
I realize you've stated a vibe is out of the question. However, the best results I and other's who have experience with Amethyst, have found a vibe, like a Lot-O or bowl type with ceramics, makes a big difference in the final results, if used after the rough 60/90 stages of a rotary............a big difference. Less additional fracturing and a more consistent, well distributed texture and even polish. And, as you are aware, Banded Amethyst makes for great cabbing material since all of the rattle and bang is taken out of the grinding and polishing process.......!
|
|
|
Post by pauls on Jun 14, 2020 16:15:34 GMT -5
Welcome to RTH from Australia.
It seems to me you are doing just about everything right. But what is causing it? Amethyst is very prone to bruising, not uncommon at all, I have never had a problem with Tiger eye so something is giving them a real thumping.
Can you slow down your barrels for polish? Fill the barrels right up, 3/4 full or more to stop any crashing. Try different fillers for polish, if you are using ceramic, try plastic, bits of leather, I have used saw dust. Try skipping the burnish, or if you feel you must run it add something to slow down the crashing, try sugar, lots of it.
See how you go, you will need to take all your bruised stuff back to at least the second stage to clean them up and run them through all the finishing stages again.
|
|
lordsorril
freely admits to licking rocks
Member since April 2020
Posts: 766
|
Post by lordsorril on Jun 15, 2020 11:08:12 GMT -5
If the bruising looks like the rock on the left you need to slow down your spin with sugar and make sure there is additional cushioning. If the bruising looks like the rock on your right then you are tumbling too many larger pieces and they are colliding with each other regardless of how much cushioning you have. Both rocks shown are smokey quartz from the same chunk.
|
|