This is Part 2 In Our 5 Part "How To Polish Rocks Series Of Instructionals. Be Sure To Check Out -
They always say “the first step is the hardest”. That is even true when learning how to polish rocks! The first grinding step to tumbling rocks into polished stones is known as the rough grind since it involves the roughest and consequently, the most abrasive of the rock tumbler grit media. In this article we'll go over the steps needed to make a successful rough grind and get your rocks on their way to becoming a beautiful polished stones.
Depending on your tumbler size, you'll fill it around 2/3 or so full with your presorted rocks for tumbling. While the amount may vary depending on experience with your tumbler and rock type, you have to fill the tumbler at least halfway. This will ensure good action or tumbling motion for the rocks. Without a good amount of action, your stones won't get a good grind from the abrasive. Once, you have the stones in the tumbler, remove them and check their weight. This will be used to calculate how much of the abrasive media to use.
Your particular abrasive should have instructions on rock weight to tumbling media amount, but a good rule of thumb for a rough grind is about .75 to one cup of abrasive for 9 pounds of rock. The rough grind is usually around an 80 grit level. With abrasives, the lower the number of the abrasive, the rougher the grind will be. For example an 80 grit level is much rougher and a more abrasive tumbler media than say a 200 grit level.
When adding the abrasive to the stones in the tumbler, be sure to tap the sides of the tumbler to get the abrasive down around all of the rocks. It is also a good idea to add in a dash of baking soda to help neutralize any buildup of gasses.
If you sorted your rocks properly and they are of a uniform size, you may need a filler to help the abrasive get in between the stones during the rock tumbling.
What happens is that uniform sized stones tend to stick together and not get ground down on all edges. Uniform size is good because it will allow you to have a consistent product, but the filler is necessary to get a good grind on all edges.
At this point you need to add enough water to just at the rock level. You want the water at the top but not over the rocks completely. In time, you will learn what works best for your tumbler, but this is the best starting point.
When the drum is finally full of stones, media, and water, you can seal it all up and crank up the tumbler. The first time you do this it is very exciting! However, it is a journey of patience so be sure to let it run without being disturbed for a t least 24 hours. After the first day, you will want to check it to check the progress and make sure you are getting a good action on the stones.
After 72 hours or so, you should hear a change in the sounds coming from the tumbler. The rough clacking that starts off will fade to a watery swoosh as the stones start the grind down. This is a good thing and means you are on the right path to a good grind. It will take about 1 week to get a good rough grind; but you may want to check the progress every 48 hours or so in order to make sure the stones are getting good action and also to release any gas buildup.
One thing to keep in mind is that if you ever have to stop the process (lose electricity or something) you might have to completely remove and wash the stones for a fresh restart. What happens is that if the process is stopped for too long, the abrasive will dry and clump and become ineffective and a real bear to clean. You should only have to do this if the batch gets stopped for a few hours or more.
If you have to do this, make sure to never dump the abrasive material down an open drain. You will need to dump it into a container and let it dry. Then, break it up and discard it. When the abrasive dries, it gets very hard and can completely ruin your plumbing. This is not a mistake you want to ever make.
Be sure to carefully wash off the stones before you start them in a fresh abrasive restart (if you have to). You don't want dried abrasive sticking to the stones and causing them to have missed grind spots after the rough grind is complete.
After a successful rough grind, remove the stones and wash them of all abrasive. Again, as in the previous paragraph, never do this over plumbing. Do this in a container where you can let the abrasive dry and be disposed of properly.
Make sure to get ALL of the abrasive off of the stones. You do not want any of the rough abrasive to contaminate the next steps. In addition, you need to inspect the stones for both a good uniform rough grind surface and for any cracks that weren't revealed before grinding. If any stones are found to be cracked, they will need to be removed from the batch and split as in the initial inspection step. Don’t get discouraged about having to remove these stones from your batch. It's all a part of the journey to a great set of polished stones.
If a lot of the stones have an inconsistent grind, or areas that didn't get ground, you will have to put them through a new rough grind process. There is no way to polish just one area of the stones.
Once the stones are finished with inspection and cleaning, set them aside to completely dry. Once they are dry, inspect them again. Sometimes cracks that are hidden by the water will show on a dry stone. Once this is complete, you'll be ready for the next step, the medium or intermediate grind! We’ll go over that step in the next article in this series -
This was Part 2 In Our 5 Part "How To Polish Rocks Series Of Instructionals. Be Sure To Check Out -