|
Post by Bob on Oct 1, 2020 12:39:49 GMT -5
From time to time I want to pass on some tips and tricks I've come up with in these 6 years of rotary tumbling.
This week, I have discovered a rare piece of chert with an agate embedded in it. This is only 3rd time in several years I've found one like this. Trouble is, the agate is in one face of the rock, and by the time the rest of the rock is shaped up in rough grind, there is a chance that most of all of the agate would be ground out--maybe all. Now, if I did manual grinding with a wheel, I could work around it to do rough shaping of this rock but all I have is the rotary tumbler. The rock is about the size of a lemon and the agate part is like a grape-size area in one face. The agate part might only go a small ways into the rock and I don't want to loose it.
So, in situations like this I put epoxy over that area to protect it. I use the 330 or 300 of whatever that lapidary one is. I seldom put it on over 1/8" thick. An area covered like this can often survive 2 weeks rough grind, so the more experience you gain doing this, the more you can judge how much epoxy.
This allows me to control when I want that agate part to be worked. In this case, I won't allow it to be touched at all in rough grind until after all other parts of the rock are done, then I will do only 1 week max after the epoxy has worn away.
The allows you to preserve the maximum amount of material on a part of a rock that you value the most. It's sort of analogous to masking off an area from painting, then removing the masking tape in order to paint that area later in a different color.
It also has another benefit at times. In this case, there is a hole in the rock, a small vug in the middle of the agate part. The epoxy filled it of course. Now, when the epoxy is ground down over the agate part it will leave a nice epoxy filled vug, usually with a very solid epoxy plug in it. Had I waited until after grinding on the rock had been done in this area, then put epoxy in that vug, the edges of the vug are already ground and rounded a bit and the epoxy plug will not hold as well, nor seal as tightly, nor look as good when the rock is done. Obviously one wants to really clean out that vug well before getting epoxy in there and use a toothpick or whatever to work it in well and get out any bubbles. I warm the rock slightly before doing this to help it flow, but not very hot otherwise the epoxy will just set too fast before it can be worked in well.
|
|
oldschoolrocker
fully equipped rock polisher
Member since January 2019
Posts: 1,578
|
Post by oldschoolrocker on Oct 1, 2020 15:53:32 GMT -5
Awesome tip! looking forward to reading more tips ot yours in the future!
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,549
|
Post by RWA3006 on Oct 10, 2020 23:00:07 GMT -5
It also has another benefit at times. In this case, there is a hole in the rock, a small vug in the middle of the agate part. The epoxy filled it of course. Now, when the epoxy is ground down over the agate part it will leave a nice epoxy filled vug, usually with a very solid epoxy plug in it. Had I waited until after grinding on the rock had been done in this area, then put epoxy in that vug, the edges of the vug are already ground and rounded a bit and the epoxy plug will not hold as well, nor seal as tightly, nor look as good when the rock is done. Obviously one wants to really clean out that vug well before getting epoxy in there and use a toothpick or whatever to work it in well and get out any bubbles. I warm the rock slightly before doing this to help it flow, but not very hot otherwise the epoxy will just set too fast before it can be worked in well. After the rock is done do you remove the epoxy, and if so, how do you get it out?
|
|
|
Post by Bob on Oct 11, 2020 11:38:41 GMT -5
No. It's clear epoxy so it looks like part of the rock when you are lucky.
|
|
rockindave
off to a rocking start
Member since May 2021
Posts: 3
|
Post by rockindave on May 21, 2021 22:53:46 GMT -5
From time to time I want to pass on some tips and tricks I've come up with in these 6 years of rotary tumbling. This week, I have discovered a rare piece of Alibates chert with an agate embedded in it. This is only 3rd time in several years I've found one like this. Trouble is, the agate is in one face of the rock, and by the time the rest of the rock is shaped up in rough grind, there is a chance that most of all of the agate would be ground out--maybe all. Now, if I did manual grinding with a wheel, I could work around it to do rough shaping of this rock but all I have is the rotary tumbler. The rock is about the size of a lemon and the agate part is like a grape-size area in one face. The agate part might only go a small ways into the rock and I don't want to loose it. So, in situations like this I put epoxy over that area to protect it. I use the 330 or 300 of whatever that lapidary one is. I seldom put it on over 1/8" thick. An area covered like this can often survive 2 weeks rough grind, so the more experience you gain doing this, the more you can judge how much epoxy. This allows me to control when I want that agate part to be worked. In this case, I won't allow it to be touched at all in rough grind until after all other parts of the rock are done, then I will do only 1 week max after the epoxy has worn away. The allows you to preserve the maximum amount of material on a part of a rock that you value the most. It's sort of analogous to masking off an area from painting, then removing the masking tape in order to paint that area later in a different color. It also has another benefit at times. In this case, there is a hole in the rock, a small vug in the middle of the agate part. The epoxy filled it of course. Now, when the epoxy is ground down over the agate part it will leave a nice epoxy filled vug, usually with a very solid epoxy plug in it. Had I waited until after grinding on the rock had been done in this area, then put epoxy in that vug, the edges of the vug are already ground and rounded a bit and the epoxy plug will not hold as well, nor seal as tightly, nor look as good when the rock is done. Obviously one wants to really clean out that vug well before getting epoxy in there and use a toothpick or whatever to work it in well and get out any bubbles. I warm the rock slightly before doing this to help it flow, but not very hot otherwise the epoxy will just set too fast before it can be worked in well.
|
|
rockindave
off to a rocking start
Member since May 2021
Posts: 3
|
Post by rockindave on May 21, 2021 22:58:28 GMT -5
Bob have you ever tried this technique using a vibe after the initial coarse rotary stage? If not, based on your considerable experience, do you think the epoxy would hold up to the finer grits in a vibe? Thanks so much. I very much enjoy reading your posts! Always learn something!!
|
|
|
Post by toiv0 on May 22, 2021 5:22:08 GMT -5
Do you have a pic of the final result. Just picked up a 4 lb piece of Alibates flint. Is this the same as the chert? Where does one get tumbling Alibates?
|
|
ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
|
Post by ericabelle on May 22, 2021 6:59:55 GMT -5
Thanks for the great tip, Bob . I will definitely be using it in the future since I have a lot of rocks that I want to tumble unevenly and plenty of rocks that have cavities! Here's a question for ya- Some of the rocks I tumble reveal little cavities of tiny quartz crystals while they are in coarse phase. Sometimes it's really pretty, and I would like to keep those crystal pockets. Do you know of any way they can be filled to go through the rest of the polishing steps, and then remove the filling after they are polished?
|
|
standles
spending too much on rocks
Well all I got was a rock ... Cool!
Member since February 2021
Posts: 325
|
Post by standles on May 22, 2021 8:15:38 GMT -5
|
|
|
Post by orrum on May 22, 2021 8:28:16 GMT -5
Alienates is off limits for collecting now. It's a Texas state park I think. Could be wrong.
|
|
|
Post by Bob on May 26, 2021 17:21:55 GMT -5
Bob have you ever tried this technique using a vibe after the initial coarse rotary stage? If not, based on your considerable experience, do you think the epoxy would hold up to the finer grits in a vibe? Thanks so much. I very much enjoy reading your posts! Always learn something!! Never have used a vibe so don't know.
|
|
|
Post by Bob on May 26, 2021 17:23:43 GMT -5
Do you have a pic of the final result. Just picked up a 4 lb piece of flint. Is this the same as the chert? Although it's often called flint it's chert. The differences are technical.
|
|
|
Post by Bob on May 26, 2021 17:25:37 GMT -5
Thanks for the great tip, Bob . I will definitely be using it in the future since I have a lot of rocks that I want to tumble unevenly and plenty of rocks that have cavities! Here's a question for ya- Some of the rocks I tumble reveal little cavities of tiny quartz crystals while they are in coarse phase. Sometimes it's really pretty, and I would like to keep those crystal pockets. Do you know of any way they can be filled to go through the rest of the polishing steps, and then remove the filling after they are polished? Removing cured epoxy sounds tough and I have never attempted it. If I use it I leave it.
|
|
|
Post by HankRocks on May 26, 2021 18:44:21 GMT -5
Thanks for the great tip, Bob . I will definitely be using it in the future since I have a lot of rocks that I want to tumble unevenly and plenty of rocks that have cavities! Here's a question for ya- Some of the rocks I tumble reveal little cavities of tiny quartz crystals while they are in coarse phase. Sometimes it's really pretty, and I would like to keep those crystal pockets. Do you know of any way they can be filled to go through the rest of the polishing steps, and then remove the filling after they are polished? How large are the crystal cavities, and are they smaller than the smallest rock you would include in the batch. If the cavities are smaller then you might not need to worry about filling them, the crystals should be mostly safe from tumbling action. Filling them with epoxy sounds like a good bit of work, ad then removing it will not be fun. And you are sure that they are quartz? and not calcite.
|
|
|
Post by toiv0 on May 26, 2021 19:58:01 GMT -5
Do you have a pic of the final result. Just picked up a 4 lb piece of Alibates flint. Is this the same as the chert? Where does one get tumbling Alibates? Although it's often called flint it's chert. The differences are technical. What is the difference between chert and flint. Interchangeable?
|
|
|
Post by Bob on May 26, 2021 22:34:14 GMT -5
Although it's often called flint it's chert. The differences are technical. What is the difference between chert and flint. Interchangeable? Rather than summarizing it here, I will let you research it or let someone else post. In the USA, most material generally called flint isn't flint if proper classification is used.
|
|
|
Post by Bob on May 26, 2021 22:38:27 GMT -5
Thanks for the great tip, Bob . I will definitely be using it in the future since I have a lot of rocks that I want to tumble unevenly and plenty of rocks that have cavities! Here's a question for ya- Some of the rocks I tumble reveal little cavities of tiny quartz crystals while they are in coarse phase. Sometimes it's really pretty, and I would like to keep those crystal pockets. Do you know of any way they can be filled to go through the rest of the polishing steps, and then remove the filling after they are polished? How large are the crystal cavities, and are they smaller than the smallest rock you would include in the batch. If the cavities are smaller then you might not need to worry about filling them, the crystals should be mostly safe from tumbling action. Filling them with epoxy sounds like a good bit of work, ad then removing it will not be fun. And you are sure that they are quartz? and not calcite. I use this method for any cavity if I for some reason don't want to cleave or saw the rock, not just because of crystalline structures. Calcite is too soft to tumble so I avoid it. Oh, the size of the cavities are generally the diameter of a pencil or smaller, and generally 1/4 to 1/2" deep. If not deeper than wide, epoxy plug will often not hold.
|
|
ericabelle
spending too much on rocks
Instagram acct: @erica_shoots_everything
Member since April 2021
Posts: 482
|
Post by ericabelle on May 27, 2021 14:39:47 GMT -5
@hankrocks , they are really small - maybe 2-3mm at most. Yeah, they are quartz - good point, they may be a little protected from the tumbling action in their pockets. I should be able to clean the grit out if any gets trapped. Thanks! Bob , yes I hadn't thought of that - I will move them on to 120/200 grit and see what happens!
|
|
|
Post by toiv0 on May 27, 2021 20:56:03 GMT -5
What is the difference between chert and flint. Interchangeable? Rather than summarizing it here, I will let you research it or let someone else post. In the USA, most material generally called flint isn't flint if proper classification is used. However, if the material comprises an artifact or is part of a rock unit that has historically been used in manufacturing weapons or tools, the name "flint" is often used. The Vanport Flint of eastern Ohio and the Alibates Flint of northern Texas are both names used for laterally extensive rock units. Native Americans mined, traded, and knapped these materials to manufacture tools for thousands of years. So while doing my homework you have me it can be used interchangeably depending on ones experience. Pretty much the same material. Tomato tomahto.
|
|
tumblee
starting to spend too much on rocks
Member since March 2021
Posts: 154
|
Post by tumblee on May 27, 2021 21:25:47 GMT -5
Got pics? Would love to see what you're working with!
|
|