The most common means is tumble polishing, but there is also vibratory finishing. To effectively polish rock in a tumbler, the stones must all be of the same approximate hardness. Rocks are placed into a tumbling barrel with varying degrees of abrasive grit and or water. Depending on the hardness of the rocks, each step in the tumbling process can take place over a number of days.
It is true that not every stone countertop has a polished finish. There are a number of finishes that stone (natural stone in particular) can have. Using the proper equipment, you can create all sorts of finishes on natural stone surfaces. Various articles like this one have been written about the various stone finishes. And they have been written about the different methods used like cut finishes and treatment finishes. One of the treatment finishes is the polished finish. It is this type of finish that we will focus on in this article. Let’s take a look at how to polish stone surfaces.
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Which stones will polish?
Most stones on the beach will not polish, but there are many that will. The harder stones polish best – those that look almost shiny already. Reject those stones which look grainy, they may be hard, but will not polish.
One way of checking the hardness of a stone is to try to scratch it with a penknife. If the knife cuts a mark or produces a powdery line, then the stone will not polish. If the knife leaves a metallic line, then the stone is harder than steel, and it will polish. This is not to say that softer stones, such as serpentine, cannot be polished, but they must only be polished with other stones of similar hardness and not mixed with harder stones.
Tumbling times will be shorter with softer stones, and a close watch will have to be kept on them, as it will not take so long to grind and polish them. Select stones that are generally 1 inch in diameter or smaller, one or two larger stones may be polished in a load that consists primarily of smaller stones.
Why polish stone?
One reason that many owners of stone surfaces choose a polished finish is that they prefer the look of a polished surface. The shiny appearance has an appeal that conveys a sense of cleanliness and newness that draws people in. Yet, the look and feel of a polished stone surface is only one reason to choose a polished stone finish.
Another common reason for choosing a polished surface is that it adds to the durability of the stone. In what way does polishing a stone’s surface contribute to its durability? The main way a polished stone is protected is it is less porous than other finish types.
Polishing a stone reduces the stone’s ability to absorb liquids in one way or another. There are a number of methods used to polish a stone surface. But each of them achieves one specific goal; they reduce the absorption of the stone. Depending on the type of stone and the liquid, this can make a huge difference in stain prevention. Since polishing stone surfaces can be accomplished in a variety of ways, let’s look at some of the methods used for polishing them.
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When Stone Polishing Is Done
As previously mentioned, stone polishing is carried out in a variety of ways using a collection of methods. Each of the methods for polishing stone surfaces happens at a different time and for a different purpose. Throughout a countertop’s lifespan, for example, it may be polished in multiple ways. Additionally, the various polishing methods will likely take place at different stages of the surface’s life. We will consider three of them.
Fabricators Polish Stone
The first time a natural stone surface is usually polished is in a fabrication facility of some sort. When the slab is cut, it often receives a polish to brighten up the surfaces so it can be shown. Usually, fab shops have machinery that is made to automate much of the work. These machines make use of polishing wheels designed for working on stone edges.
When a stone countertop is being cut and shaped for a particular kitchen or business area, it gets polished again by fabricators. This might be on the edges and corners after the slab is cut. There are other times when stone materials like granite and marble may be polished by fabricators as well. For example, at the install location when the installers want to touch up a countertop or other surface, they have just installed.
Restorative Stone Polishing
Another point in time that stone surfaces are regularly polished is once they have been installed and used for several years. Natural stone is a durable material and will last decades with proper care and maintenance. Yet, the surface of a polished stone can become dull looking after years of normal use.
The everyday wear and tear of a kitchen counter can cause your surface to lose the lustre it had when it was first installed. Thus, stone owners often restore the polish or have it renewed by either performing or hiring some to perform a restorative polish on the stone.
Whether restorative polishing is necessary is based on the number of years the stone has been used and to what degree the surface has been used. Additionally, the need for this kind of polishing is oftentimes a matter of personal preference.
Routinely Polishing Stone
Most frequently, the stone is polished as part of a routine on a regular basis. Making sure that a stone has a fresh shine can be done relatively easily. This process is easy and can be regularly achieved by the stone owner. Whether it is weekly, daily, or monthly, this method of polishing stone works based on the fact that adding lustre a little at a time regularly maintains the shine and polish of the surface.
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Stone Polishing Techniques
Now that we have talked about the timing of stone polishing as it relates to a stone’s life, we will discuss the ways that stone surfaces can be polished. These methods are performed by various persons and can happen at various times, but the method is what we want to focus on in this section of the article.
Stone Polishing Pads
As we mentioned earlier, much of a stone’s polish comes from stone professionals when preparing a slab or surface for purchase and installation. One of the main ways that a stone surface is polished is through the use of polishing pads.
Using granite polishing pads and other pads to polish the stone, a fabricator can progressively smooth out the surface of the material until the shiny look is achieved. Polishing pads for stone materials are a lot like sandpaper is for wood. The person polishing the stone begins with a pad that has a coarse grit. Each additional pad has a higher grit than the previous one. As the grit increases, the shine improves until finally, a full polish is achieved.
Polishing pads come in a variety of types and are available in a number of steps. 3 Step, 5 Step, and 7 Step polishing pads are common in the stone industry. Pads are commonly sold for dry environments as well as wet only environments. Finally, polishing pads are designed to polish specific types of stone, including:
- Natural Stone
- Light Materials
- Dark Materials
- Engineered Stone
Most polishing done with pads will be before a stone surface arrives in the final location at the time of install. Yet, there may be times when polishing pads are used after the installation is complete.
Polishing Powder For Stone
When restoration of stone surfaces are needed, the polishing powder can be used in conjunction with polishing pads. Using a polishing powder (a.k.a. polishing compound) removes minor scratches and stains from the surface of the stone. This restores the lustre of the surface and reduces the dull appearance that can result from years of normal wear and tear that comes from day-to-day use.
Using a stone polishing compound to revitalize the shine of your polished stone surface can be done by the stone owner or by a professional. In either case, specific tools for restoring stone will be needed. Because of this, owners often decide to hire a professional to do the work of restoring natural stone.
Fortified Stone Polish
Tools and powders work well for the types of polishing that they are made to perform. Yet, another easy way to polish stone surfaces is to make use of a fortified stone polish that is designed to maintain the polish. This kind of polish is applied by means of a sprayer. Aerosol and pump sprayers are among the applicators. Tenax distributors provide a range of stone maintenance products. By following a stone maintenance routine, less restorative polishing may be needed.
Tips on Stone Polishing:
Grind wet. Always grind wet to protect your lungs from breathing in the dust from stone polishing. The dust from some stones, such as malachite, is quite toxic. In addition, wet grinding eliminates damage to expensive diamond wheels and stone-polishing tools.
Judge dry. Although we always grind wet, we recommend that you always dry the stone completely before judging its surface. Water on the stone surface will only hide scratches and give a false reading.
Use the whole wheel. Use the entire width of the grinding wheel, not just the centre. This will ensure a longer life and better performance for your diamond wheel.
Skip no grit. Work sequentially from the coarsest to the finest grit. Don’t be tempted to take a short cut by skipping a grit in order to save a little time. The progression through finer and finer grits is necessary to remove the scratches left by the previous grit. The goal is to have the scratches become finer with each grit size until they can no longer be seen. Our experience has been that if you skip a grit, the final polish will show big scratches.
You will wonder where those scratches just came from! The truth is that they were there all the time, but you didn’t sand them out when you were supposed to. If you skip a grit and find deep scratches, you’ll have to go back three or four grits to remove them. It’s always faster to do it right the first time than to try to take shortcuts and risk damaging the stone you’re working on.
Polish slow. Polishing is the final step. There is a myriad of polish and stone-polishing pad combinations; our preference is charging a soft leather pad with a thin paste of Holy Cow stone polishing compound and water. The actual polishing occurs as the pad starts to dry, and the stone starts to pull against the surface. We keep the speed of the pad low to eliminate any heat buildup.
Keep it clean. Remember, “Cleanliness is next to Godliness” is especially important when it comes to lapidary work. To prevent cross-contamination from coarse grits, we are careful to rinse the stone and our hands at every grit change during stone polishing. We also thoroughly clean our machines after each grinding session to prevent contamination when moving through grit levels. Polishing compounds and wheels should be kept in sealed plastic containers when not in use.
Believe what you see. Your eyes are your most important tools when it comes to stone polishing. They are your feedback loop. If your eyes tell you that something is not quite right about the surface, believe them. Stop! Figure out what the problem is before continuing, and think through the steps you’ll take to remedy it before you begin.
Grind a little and look a lot. This is the mantra of successful lapidary. Taking your time and being very observant during the polishing process is essential to secure the results you want.
Step by step rock polishing instructions
Open the barrel by pushing either end cap off with your thumbs. When new they are sometimes tight, but if you immerse the barrel in hot water they can be easily removed. Squeezing one side of the barrel assists when opening. If you use warm water to fill the barrel, it will help to suck on the lid.
- Fill barrel ¾ full with stones and shake to settle. Do not useless, it will not work as there is no tumbling action unless the barrel is filled sufficiently.
- Add water to just over the top of the stones.
- Add one heaped tablespoon of coarse silicon carbide 80grit for a 1 ½ lb barrel or two heaped tablespoons for a 3lb barrel and three heaped tablespoons for a 5 lb barrel.
- Run the machine for a few days and nights while occasionally examining the stones. Fairly smooth pebbles might need only about three days to become nicely rounded while very jagged ones may need ten or more days running and the grit topping up to get the same effect. Seven days is a reasonable average.
- Thoroughly clean the stones and barrel by removing both ends.
- Proceed as before using 220 grit this time. It should only be necessary to run this grade for about 5-6 days.
- Thoroughly clean stones and barrel by removing both end caps, washing carefully.
- Proceed as before using the same proportions of grit and water but this time use 400 grit. Please note this stage is very significant and determines the final polish; it is vital you do not cut it short.
- Allow at least seven days of tumbling. Do not top up with fresh grit as this will re roughen the stones. Each day on this stage imparts a smoother finish as the grit breaks down and progressively smoothes the stones making it far simpler for the next stage.
- Very, very thoroughly clean the stones and barrel. It would be useful to keep one barrel to be used specifically for polishing only, because of the difficulty of cleaning grits completely from the sides of the barrel. Additional barrels may be purchased separately. Examine the stones very carefully and make sure that they are very smooth. Discard any stones that are badly cracked or have jagged edges- they can be re tumbled with your next load.
- Repeat steps as before using similar amounts of water but one level tablespoon of cerium oxide instead of grit for a 1 ½ lb barrel (adjust amounts accordingly for the size of the barrel as with the grits). If the barrel has been cleaned out properly and the previous steps are carried out correctly seven days running should produce gleaming stones! Remember, as with all things practise makes perfect.
Do not put any of the resulting slurries down the sink – it is inclined to set solid!
These expert stone-polishing tips will help you create better gems and cabs for your metal jewellery-making designs. However, there’s a lot to learn before these tips can be applied.
As we have seen, there are a number of ways to polish a stone surface. And we have looked at the benefits of a polished stone countertop. Whether it is using equipment, powder or liquid, or pads with a polishing substance, the shine you get from a polished surface is just one of the benefits.