The process of tumbling rocks in order to achieve beautifully polished stones that are either round or angular in shape is something that will require patience, the right type of equipment and, of course, rocks, these rocks are also commonly referred to as “rough” before the process of tumbling has started.
For many people, a visit to the beach is a great opportunity to look for beautiful shells, stones or pebbles, finding a smooth and rounded rock or two is wonderfully satisfying, especially if they have particularly nice markings or colors. These nicely rounded and smooth stones have become like this through the process of tumbling; as the tide washes in and out, the rocks are tumbled back and forth in the sand over and over again, and over time, perhaps even thousands of years, any jagged edges or odd shapes are rounded off and smoothed out.
Rock tumbling with a rotary rock tumbler follows the same process as the ocean tides but the results are achieved within just a few weeks rather than many, many years.
How long it will take to tumble rocks until they reach the desired end result will depend upon a number of factors, including the type of tumbler used, the type of tumbling grit, the type of rock that is being tumbled and the required result. This article will cover each of these factors to assist you in making the right choices when it comes to this fascinating and addictive hobby that is also known as lapidary. You should be aware though, rock tumbling is a very slow pastime and achieving the desired results, either with a rotary tumbler or a vibratory tumbler, is going to require a great deal of patience. This is something that you should definitely consider carefully before you invest your hard earned dollars in this captivating hobby. For those who have fallen under the spell of rock tumbling, the amount of time it takes is completely unimportant, it is all part of the process and if it takes longer than expected, then so be it, the anticipation is half the fun! Many people who take up the hobby of rock tumbling find that they widen their interest in the subject and become generally absorbed in geology, the knowledge they gain can help them in their hobby and their search for rare and beautiful rocks. People who search for rocks (rough) are affectionately known as rock hounds. The acquisition of the rough form of rocks is another time factor that should be taken into consideration when making the decision of whether to invest in the pastime of rock tumbling or not. Rocks for tumbling are widely available in lapidary outlets, both in store and online, this is the easy way to obtain rough rocks and is probably the best route for beginners in the subject, the rock types will be identified and the supplier will generally be able to offer advice to anyone starting out in rock tumbling. For those experienced in rock tumbling or for the purists, searching for rocks is an integral part of the whole process, the search is the starting point for those who are known as rock hounds.
What is a rock tumbler?
In order to tumble rocks, you will require a rock tumbler, a rock tumbler is a piece of equipment that is generally either a cylindrical barrel that rotates or a bowl that is shaken by a motor, these are the most commonly used rock tumblers and this article will concentrate upon these two types. Both types of rock tumblers work by collision, abrasion and friction in order to produce smoothly polished stones, this is done by placing rough rocks into the tumbler, along with tumbling grit and a little water. The rotary tumbler will rotate the contents whereas the vibratory tumbler will shake them, after time the friction caused by this process will smooth and polish the rocks.
How long does rock tumbling take using a rotary rock tumbler?
Rotary rock tumblers are the most commonly used type of tumbler, with this version of rock tumbler the rocks are sealed in a cylindrical barrel that is made of plastic or rubber, they can also be made of rubber lined plastic or metal. In the early days of rock tumblers, they were often made of old paint cans. Generally, rock tumbling using a rotary rock tumbler takes around four to eight weeks, as previously mentioned, this will depend upon a number of factors, including the type of rock, the type of grit and how picky you are about the end result. For most people, rotary rock tumbling consists of four stages, these stages are:
Coarse grind
The coarse grind stage of rock tumbling with a rotary rock tumbler uses a man-made silicon carbide abrasive grit, this stage uses larger particles in order to roughly shape the rock. Coarse grit is typically known as 60/90 grit. This phase can take a week, although it generally takes longer with most people, usually two to four weeks.
Medium grind
The medium grind stage of rock tumbling with a rotary rock tumbler also uses man-made silicon carbide abrasive grit, although for this stage the particles are smaller. The medium grind stage removes any scratches that have been caused by the coarse grind stage, it also starts to give the rock a smoother appearance. Medium grit is typically known as 150/220 grit. This phase can also take a week, it will depend upon the type of rocks being tumbled and how picky you are.
Fine grind
The fine grind stage of rock tumbling with a rotary rock tumbler uses the same man-made silicon carbide abrasive grit, this stage uses the finest particles of grit. The fine grind stage continues the smoothing process prior to the polishing stage, this stage is often called the pre-polish stage. Fine grit is typically known as 500 grit. As with the previous two phases, the find grind stage can take a week but some people like to run it longer.
Polish
There are a variety of materials that can be used for the polishing stage of rock tumbling with a rotary rock tumbler, it really is down to personal choice so the best way to discover your own preference is to experiment. The medium used for the polishing stage of rock tumbling is generally known as rock polish and examples are TXP aluminum oxide and Cerium oxide. The polishing stage can take a week, although that will depend upon your personal preference.
As previously mentioned, each of these stages can take just a week, this means that a full cycle of rock tumbling using a rotary tumbler can be complete in only four weeks, however, most people prefer to run the first stage (coarse grind) for at least two weeks and maybe even longer if they feel that the results are not good enough. Each stage can be run for as long as you wish, in order to gain the desired results.
How long does rock tumbling take using a vibratory rock tumbler?
Vibratory tumblers, although popular, are not as commonly used, the most likely cause of this is because they are about 50% more expensive to purchase. That said, rock tumbling with a vibratory tumbler is a much faster process, so you will save on your running costs.
A vibratory tumbler does exactly what its name suggests, it vibrates – or shakes, the rocks. The shaking motion causes friction between the rocks and the grit which smooths out any imperfections, it should be noted that a vibratory tumbler will not round the rocks like a rotary tumbler.
A vibratory rock tumbler can generally smooth and polish rocks in about half the time that a rotary rock tumbler will take, this will save on your energy costs and produce a beautifully finished product for anyone who prefers an angular shaped rock rather than a rounded specimen, or for those who do not have the patience to wait for the longer rotary tumbling process.
The tumbling stages of both types of rock tumbler are similar, except that you can skip the first phase and reduce the process time of the subsequent phases. As before, the time it will take to reach the desired results using a vibratory rock tumbler will depend upon the types of rocks and how picky you are. We have listed the stages that are generally taken when using a vibratory rock tumbler below:
Coarse grind
This stage can be skipped when using a vibratory rock tumbler
Medium grind
This stage can last from as little as 3 days to a week
Fine grind – also known as pre-polish
This stage can take only 2 to 3 days
Polish
This stage can also take only 2 to 3 days
As you can see, the process of rock tumbling when using a vibratory rock tumbler is much faster than when using a rotary rock tumbler.
Can I Use a rotary rock tumbler and a vibratory rock tumbler?
Yes you can, in fact many people prefer to use both types of tumblers in order to achieve rounded rocks in a faster time than when just using a rotary rock tumbler. For this method you should tumble your rocks in a rotary rock tumbler for one to three or four weeks until you reach the desired results and then finish the process with the three stages of the vibratory rock tumbling method.
Burnishing
After the four stage process of rock tumbling with a rotary rock tumbler, a vibratory tumbler, or a mix of both types of tumblers, your stones should be beautifully smooth with a rounded shape, their surface should also have a shine, in fact they should look the same as they do when they are wet. If you are not happy with the shine then you can add a further stage to the process, this stage is called burnishing and it can enhance the final finish of your tumbled stones considerably.
The burnishing process uses powdered detergent, such as Dreft or Tide, other suitable products are Ivory soap that has either been grated or sliced very thinly, or Borax. It is crucial that you NEVER use dishwasher powder or liquid detergent, you should also never use any type of product that may contain any bleach, oils, perfumes or any other kind of additives as this may lessen the effectiveness of the burnishing product, cause scratching or dulling of the stones or even damage the rock tumbling barrel.
To wrap it up, rock tumbling is a wonderful and fascinating way to spend your leisure time, however, it is definitely not a hobby for anyone who seeks instant gratification. For those with the patience, diligence and perseverance, the slow process of rock tumbling can be a hugely rewarding pastime.