How to get the entire rock polished properly?

[calura]

I finished the very first batch of tumbling. This was a sample collection that came with the tumbler, so there were many different types of rocks in there. At first they were too "dirty" to really tell which was which, so yes I put them all in together.



My problem is that the polishing phase missed a lot. Specifically, it missed larger almost-flat sides, although those sides were slightly concave. It's like the corners and pieces that stick out were the only things to strike any surface and actually get polished. What is the best way to prevent this and get those larger areas polished properly?

Here are photos of the polished rocks. The first photo shows several and it's actually easier to see the issue on the ones near the top of the photo.

[jasoninsd]

My guess is you didn't have enough "smalls" in the batch. Could be small rocks (like REAL small) or ceramic media...

[pebblesky]

What are your steps of polishing? Do you finish the polishing step in a vibe or in a rotary? Assuming you have proper polish powder (such as rockshed.com/rock-shop/rock-tumblers-supplies/rock-tumbling-grit-and-accessories/aluminum-oxide-polish/), you might want to put more small and round fillers to help the polishing procedure to be more efficient.

[calura]

Jul 14, 2024 21:15:28 GMT -5 pebblesky said:

What are your steps of polishing? Do you finish the polishing step in a vibe or in a rotary? Assuming you have proper polish powder (such as rockshed.com/rock-shop/rock-tumblers-supplies/rock-tumbling-grit-and-accessories/aluminum-oxide-polish/), you might want to put more small and round fillers to help the polishing procedure to be more efficient.

All of mine are done in rotary. Its all I have. Many of the rocks did turn into tiny pieces by the end - my husband was actually disappointed by that. The tiny piece in the first photo was one of at least a dozen. So probably at least 1/3rd of the mix was that size. Maybe I just needed to polish longer?

I only used the grit packets that came with the kit. All four stages, at recommended lengths of time. Although tomorrow I have a full set of 5lb jars of grit coming in with 2.5 lbs of polish, all from rocktumbler.com, so I assume that would be "correct" grit too?

[knave]

Picture stage 1 as the most important, longest stage. The most successful tumblers leave rocks in this stage until they are defect-free. This could be as short as one week or as long as 3 months. Keep running stage one, on your weekly checkup, take out “ready rocks” and add new material until you have enough good ones for a batch of stage 2.

[HankRocks]

You said that some of the rocks turned into smaller pieces. I suspect that means that some of the rocks were soft and ground away or they were susceptible to breakage. The mixture of hard and softer rocks is not a good batch. Also as a couple of folks mentioned what some of the polish that comes with some of these tumbler grit packs is not a good polish. It's more of a good pre-polish. Something along the lines of 12,000 Aluminum Oxide is considered a good polish. I use Tin Oxide, which is an excellent polish but very expensive.

The more difficult surfaces to tumble polish is flat or almost flat surfaces. I rotary tumble polish slabs of all sizes up to almost 6" by 5". The batches batches usually consist of half slab and half pea gravel and trim saw scraps. Polishing is done by collisions between rocks with polish slurry in being pressured by the rocks. The rounder surfaces will have more "roll" as I call it, they stay in contact with their neighbor a bit longer hence more polish action. That also why a mixture of sizes is important, more rock to rock contacts. Even then the edges of the slabs polish much quicker than the flat surface.

Henry

[calura]

Jul 15, 2024 6:12:48 GMT -5 HankRocks said:

 The mixture of hard and softer rocks is not a good batch.

I'm aware of this, but it was the pack that came with the tumbler and I couldn't see them well enough (without breaking most of them) to tell what they actually were. Even after pre-rinsing, most of them seemed to be covered in white or grey material that covered the "designs" of the rock so I couldn't tell.

[calura]

Jul 15, 2024 5:10:51 GMT -5 knave said:

Picture stage 1 as the most important, longest stage. The most successful tumblers leave rocks in this stage until they are defect-free. This could be as short as one week or as long as 3 months. Keep running stage one, on your weekly checkup, take out “ready rocks” and add new material until you have enough good ones for a batch of stage 2.

I don't see how this information applies to my question?

[pebblesky]

Jul 15, 2024 2:07:32 GMT -5 calura said:

Jul 14, 2024 21:15:28 GMT -5 pebblesky said:

What are your steps of polishing? Do you finish the polishing step in a vibe or in a rotary? Assuming you have proper polish powder (such as rockshed.com/rock-shop/rock-tumblers-supplies/rock-tumbling-grit-and-accessories/aluminum-oxide-polish/), you might want to put more small and round fillers to help the polishing procedure to be more efficient.

All of mine are done in rotary. Its all I have. Many of the rocks did turn into tiny pieces by the end - my husband was actually disappointed by that. The tiny piece in the first photo was one of at least a dozen. So probably at least 1/3rd of the mix was that size. Maybe I just needed to polish longer?

I only used the grit packets that came with the kit. All four stages, at recommended lengths of time. Although tomorrow I have a full set of 5lb jars of grit coming in with 2.5 lbs of polish, all from rocktumbler.com, so I assume that would be "correct" grit too?

I would assume you are using a 3lb barrel. By "turn into tiny pieces" do you mean some pieces broke into several smaller pieces or some pieces grind really fast during tumbling?

Like what HankRocks said, the flat surfaces take longer to polish. During my polishing cycles in the vibe, after the first day when I take pieces out to examine, the corners and the edges are already very shiny and the flat surfaces are not, so I will give the batch a couple more days to polish if there are are lot of flat surfaces in the batch. I would guess an extra half week to a week in the rotary will help the polish.

And when we talk about small fillers, they are meant to be truly small, and we need a lot of them, about 1/3 of the volume of all the rocks, not 1/3 of the numbers. These small fillers are most important for pre-polish and polish steps. I have set aside a bag of small fillers exclusively for the polish stages so I don't worry about contamination and these small fillers don't get smaller quickly.

[pebblesky]

Please tell your husband, in order to improve the results, more tumblers and more rocks are on the way 

[calura]

Jul 15, 2024 12:12:01 GMT -5 pebblesky said:

Please tell your husband, in order to improve the results, more tumblers and more rocks are on the way 

You assume he isn't planning to buy it all himself! Lol! He LOVES this hobby!

So our tumbler did come with a little packet of plastic beads. Would that have been a good moment to use them, then?

I did get my new box of polish in, so I guess I should toss the rocks back in for more stage 4 with polishing medium and the plastic beads?

[titaniumkid]

Your plan sounds good.

After about 7 days, you can take a couple of rocks out (if you can get some of the problematic ones, that would be great), give them a rinse and dry, and check the polish. If they aren't quite right, you can always leave them in polish for another week. I found that helped. It is a bit risky because polish slurry is not as thick as grit slurry, so they may knock around more and could potentially bruise, but if you have something in there like plastic beads they should be cushioned.

[python]

Is your tumbler one of the types that has multiple speeds?

If so, try these things:

Always use the lowest speed and forget about the other two speeds.

Be sure to fill the barrel to 3/4 full on all stages. If you don't have enough rocks to do so, get ceramic media and use it to supplement the space to get it to that level.

For stage 1, run for 3 days and repeat as necessary to get the rocks shaped how you want them.
Stage 2, run for 3 days once.
Stage 3, run for 7-10 days once.
Stage 4, run for 7-10 days once.

Use Silicone Carbide grit in stages 1 and 2.
Use Aluminum Oxide grit in stages 3 and 4.

Be sure to rinse the rocks very well between stages. And I suggest running a burnishing/cleaning cycle using Borax or soap after stage 3 and stage 4.

Use less water than the instructions say to. Do not cover the rocks with water. The water should be around 1/2 inch below the rocks. This will make the slurry a little thicker so that the grit sticks to the rocks. You could also try putting in 1 tbsp of Borax with the grit to thicken the slurry and make it stick to the rocks better.

Hope this helps!

[moocks]

In order to polish something involves a few steps with ever decreasing size grits. If you don't get the imperfections or scratches out from the preceding step you will never achieve a good polish. That goes for the flats doubly. The points are almost always in contact and that is why they polish better. When you add ceramic media to your tumbler you add many small points and they help grind out the previous stages scratches on those flat areas (and also the imperfections). Maybe add media to your mix....

[nantucketdink]

I think you figured out one of the key elements in your first batch. Do not move your rocks out of stage 1 until the rocks are fully rounded and imperfection free so all surfaces are easily exposed during the rest of your stages. It will make the rest of the process super easy.

[bobnchris]

Jul 15, 2024 11:28:42 GMT -5 calura said:

Jul 15, 2024 5:10:51 GMT -5 knave said:

Picture stage 1 as the most important, longest stage. The most successful tumblers leave rocks in this stage until they are defect-free. This could be as short as one week or as long as 3 months. Keep running stage one, on your weekly checkup, take out “ready rocks” and add new material until you have enough good ones for a batch of stage 2.

I don't see how this information applies to my question?

It applies directly to your situation because if you don't get all the defects out of your rocks, and get them 100% convex, then you will not get them blemish free in the end.

[parfive]

Aug 29, 2024 21:42:37 GMT -5 bobnchris said:

It applies directly to your situation because if you don't get all the defects out of your rocks, and get them 100% convex, then you will not get them blemish free in the end.

I’ll contradict that. The tumbling wizards here at RTH polish concave stuff all the time.         : )