5 Things to Know Before Buying Alumina ceramic sands

Article Sections

• Introduction
• What makes sandpaper so abrasive?
• Why you should care about the abrasive grain you choose for your project.
• Aluminum Oxide ' The Versatile Powerhouse of Abrasives
• Silicon Carbide ' Self-Sharpening And Great For Beautiful Finishes And Glass
• Ceramic Alumina ' Long Lasting, Great For Metal Finishing
• Alumina-Zirconia ' The Grittiest Of Them All           
• Conclusion
• Abrasive Grains Cheat Sheet

Introduction

If you're looking to create the best version of your woodworking or metal projects, no doubt sanding will be a key part of that process, whether you're rough sanding to remove jagged edges, de-burr, in preparation for gluing, or if you are in the finishing and polishing stages.

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Each of these steps clearly requires different sandpaper grits to get the best results, but the grain type will also impact your overall results ' and believe it or not, it may even be best to change types depending on the material you're working with and the stage you're at. So, clearly, choosing the right type of abrasive will be critical, and could mean the difference between a high-quality finished product and an amateurish-looking piece, in addition to increasing the life of your sandpaper, getting the best results for your sanding/polishing/finishing stage, having a faster, cleaner and cooler (reduced heat/friction) sanding job.

But, what to pick? It can certainly be overwhelming to choose, once you start to look into all the types of coated abrasives on the market (not to mention just on our website!), even if you're an experienced sander. In this article and accompanying materials, we'll detail the most common abrasive grains we offer and some of the conditions and materials that they work best for. 

And, if you're more of a visual learner, skip to the bottom of this article and download the infographic with all this information.

(Note that most of these products are fairly versatile, designed in a lab for particular conditions and you may have other factors to consider, such as budget, time and versatility of materials/projects, type of sanding process/machine, product format requirements, so use this only as a guide ' don't take it as gospel.)

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So, wait' If it's not actually sand, what makes it so abrasive?

If you're reading this article, it may not come as much of a surprise to you that the term 'sandpaper' is actually a misnomer, as the grittiness of sandpaper is not actually made from sand, like at the beach, and this grit is not always even attached to paper.

So, if it's not actual sand, then what is it? And, what are the differences between the various abrasive materials?

Sandpaper is actually a type of coated abrasive, meaning, it is made from some type of abrasive 'grain', such as the types we are going into in this article, which is affixed to some kind of backing ' often paper, cloth, plastic, or even foam sponges or mesh. There may or may not be other added fillers or coatings, such as stearation.

These days, there are several types of abrasive materials used on sandpaper products, including a few natural rocks/minerals and a handful of synthetic substances, manufactured in labs, each with their own advantages and disadvantages.

The most common natural minerals used in abrasives are emery and garnet, while four common manmade types are silicon carbide, aluminum oxide, ceramic alumina and alumina- zirconia. Each varies in longevity, coarseness/aggressiveness, amount of friction required, friability, cost, ideal application, available grit sizes and coating and what formats of products they are available on, such as disks, sheets, or belts.

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Why you should care about the abrasive grain you choose for your project.

Before we discuss each of these grains, it's important to consider why these characteristics matter. First, and let's be real, does anyone really enjoy sanding? If you do, let us know!! 'But for the rest of us, sanding can be a bit time consuming, boring and even a pain on the hands, so, wouldn't it be great if we could make the process more efficient, and more effective? Other than making it merely tolerable with some headphones and great music, we can often speed up the process by using the proper type of abrasive product for our application with proper technique, which will save time and resources.

Additionally, using the proper abrasive grain / project material combination, as well as proper technique and pressure, can also help to reduce sanding costs by allowing your products to last longer. One way this happens is thanks to using products that create less friction, and therefore less heat, which causes the abrasives to cut more effectively, not burn your material and clog up less. Furthermore, the friability, or the characteristic that allows grains to break to form new, sharp edges (self-sharpening), allows you to go longer before the sandpaper wears out.

Now that you know why it's important to choose the right grain for the project, let's discuss each of the four options we have available.

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Aluminum Oxide ' The Versatile Powerhouse of Abrasives

The most versatile of the synthetic abrasive grains, Aluminum Oxide commonly comes in three types: pink, white and brown, or semi-friable. Aluminum oxide is a chemical compound of aluminum and oxygen formed by fusion and then broken down and sorted by grit size through a series of mesh screens (see this video for an example). Each of the types measures at about 9 on the Mohs Hardness Scale, a measurement scale that defines how resistant materials are to scratching. The Mohs scale places common minerals on a scale of one through ten, starting with Talc at the bottom and Diamond at ten. 

Most of the time, the type of aluminum oxide will not be mentioned on our website, however each type is more suitable for different types of sanding.

Aluminum oxide-based coated abrasives can be used in belt sanding, power sanding or for hand sanding applications, and are available on a range of backing materials with both open and closed coatings.

Pink

Pink aluminum oxide is available in coarse through fine grit products on a variety of different backings and in a variety of formats. It generally works well for softer substrates, such as wood, for aggressive sanding.

White

White aluminum oxide is available in coarse through fine grit products on a variety of different backings and in a variety of formats. It generally works well for wood, providing a cooler sanding experience for aggressive sanding on wood and lacquers, as well as for use between coats of finish on your woodworking projects.

Brown/Semi-friable

Brown, or semi-friable, aluminum oxide is the most common type of aluminum oxide, because of its versatility. It is available in coarse through micro grit products, coming affixed to a variety of different backings and in a variety of formats. It generally works well for harder substrates, such as metal (particularly softer metals), fiberglass, drywall, painted/primed surfaces and wood. When used in coarser grits, from 80 to 180, with a medium pressure/tension, this grain works well for wood and metal stock removal, allowing the grains to break and re-sharpen, making the product last longer. When used in finer grits, around 600-800, this material is great for finishing and polishing metal.

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Silicon Carbide ' Self-Sharpening And Great For Beautiful Finishes And Glass

Silicon Carbide, another popular grain type, is a semiconductor containing silicon and carbon and is produced through carbothermal reduction. It is the hardest common abrasive grain, other than diamond, and measures at a 9.5 on the Mohs Scale of Hardness.

While silicon carbide tends to wear quicker than aluminum oxide, it is also sharper and more friable, therefore it is still a long-lasting product and is ideal for uses on harder materials, rougher surfaces, and for polishing, due to its hardness and sharpness. It is best for metals (particularly harder metals) and is the only grain that can be used on glass, stone and marble. Silicon carbide is also effective on MDF and cork.

Silicon carbide is frequently used in wet sanding applications, such as polishing stone and marble, as well as automotive polishing applications. In coarser grits, this abrasive is good for removing rust, deburring metal and glass, refinishing wood flooring (cutting through/removing old finish). Silicon carbide can also be used to sand between finishing coats in woodworking projects, so it is common to use aluminum oxide for rough sanding of raw wood, and switch to silicon carbide when in the finishing stages of the same project.

Being a pretty versatile, and relatively forgiving, abrasive grain, silicon carbide is available on belts, disks, sheets, sponges and for use in power sanding and hand sanding applications.

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Ceramic Alumina ' Long Lasting, Great For Metal Finishing

Ceramic alumina is a long-lasting synthetic grain produced directly as a grain through an aqueous dispersion of fine aluminum oxide powder. While it can often be more expensive, it lasts longer and provides a cooler sanding experience than aluminum oxide. Often simply referred to as ceramic, this grain works best on metal, stainless steel in particular, and requires a hard surface/pressure in order to activate the friability. While it can be used on wood, it will be very aggressive ploughing through the wood instead of cutting it.  This could lead to a very uneven scratch pattern which will result in a poor finish.

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Alumina-Zirconia ' The Grittiest Of Them All             

Alumina-Zirconia, also referred to as zirc or zirconium, is produced by die-casting and is typically available in only coarser grits, up to 120, on belts and disks for power sanding units. Because this grain is best for heavy stock removal in mills, an initial sanding of raw woods, and removing burrs from very hard metals, it is mostly available on heavy cloth backings with mostly open coats, to provide a sturdy product with space for a lot of material to accumulate. This allows the products to withstand medium to high pressure and avoid clogging too quickly. If you have a lot of rough sanding to do for raw woods, rust or other metal work, choosing zirconia might be the best option, in spite of a potentially higher price, because it will last longer, be more friable, and provide a cooler sanding experience than aluminum oxide.

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Contact us to discuss your requirements of Alumina ceramic sands. Our experienced sales team can help you identify the options that best suit your needs.

Conclusion

As you can see, there are certainly many aspects that will influence which abrasive grain, and therefore, which 'sandpaper' will be best for your particular application. While aluminum oxide is the most common, and generally most affordable of our products, choosing another material, or combination of materials and grits, might ultimately be more cost effective, longer lasting and even more effective at the job, even if you only work with one base material. For instance, if you are someone that frequently works with jagged wood, bringing it all the way to a finish, or if you work with reclaimed metal parts for cars, it may make sense to mix, therefore, choosing different grains for coarser applications verses finishing and polishing.

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Abrasive Grains Cheat Sheet

Here is a sample of a great infographic, designed to help make all this information much simpler, and easier to understand.

If you would like further information or assistance, we welcome you to contact our customer service or sales representatives.

There are a lot of different abrasive grain types and each job may require different abrasive material.  We've posted an article in the past about some of the different abrasives, mainly comparing ceramic vs zirconia abrasives, but we'd like to discuss these red colored ceramic abrasives at more length for you.

This particular abrasive grain is the newest material created for the abrasive industry.  Ceramic alumina is not found in nature.  It is what you call an artificial or manufactured abrasive since it's been created through man-made/scientific means.  Through this innovation, ceramics have been found to be a superior abrasive for many applications.

What is a Manufactured/Artificial Abrasive?

This isn't that important to know when buying ceramic abrasives, but we're including this information for those of you interested in the nitty-gritty scientific details of how things are made. 

Natural abrasives like garnet and emery are found in nature, hence the "natural" abrasives name.  Artificial abrasives were created scientifically through different processed, creating all new materials that have qualities that natural products aren't capable of.  So then, how is ceramic alumina made?

The process of making ceramic abrasives involves a chemical procedure of creating a colloidal solution, sol, that contains tiny particles of aluminum oxide in a liquid medium.  For an easy visual, think of mud.  Dry mud is just tiny pieces of dirt, but mixed with water it becomes a liquid-like structure that still contains all of those tiny dirt pieces. 

The sol-gel process is what forms many metal oxides such as silicon, titanium, and ceramic alumina.  For ceramic alumina, bits aluminum oxide alloy is suspended in the sol mixture.  As it dries under controlled temperature, the minerals will separate from the binding agent.  

The final step is called sintering, which is another heat treatment that causes the aluminum oxide powder grains, or crystals, to shrink and become denser and stronger.  During this process, individual crystals combine to create a polycrystalline material with larger grit sizes.

How Tough are Ceramics?

Ceramic abrasives are some of the strongest and sharpest abrasives currently on the market.  

Ceramics are a friable abrasive, meaning that as the product is being used, tiny pieces of the grit will fracture off exposing fresh sharp material.  This helps the ceramic abrasives constantly renew the surface to provide a consistent cutting and grinding action for a longer period of time.  

Ceramic sandpaper and other abrasives are strong enough to cut and grind most metal surfaces such as carbon steel, aerospace alloys, titanium alloy, aluminum, ferrous metals, and nonferrous metals.

When you use it on superalloys and stainless steel it will perform better than most other abrasives. Ceramic will not dull as quickly due to its extreme toughness and self-sharpening abilities. That level of toughness will allow ceramic abrasives to provide outstanding grinding and finishing performance on a variety of different hard metals. 

How can you Use Ceramic?

Ceramic abrasives have become a favorite among knifemakers, auto body workers, and metal fabricators.  It is commonly used in aerospace applications as well as blasting, blending, burnishing, cleaning, surface preparation, and abrasive jet cutting to name a few. 

Depending on the task at hand and the tool you prefer, there is a wide variety of ceramic aluminum oxide abrasive choices. Ceramics are available in products like the Black Hawk Abrasives 2' Quick Change Ceramic Disc for those hard to reach corners to even 12" Ceramic PSA Sanding Dics. As ceramic becomes more common in the market it is easy to find things like 6' x 48' Ceramic Sanding belt, which has become one of our top selling belts in ceramics as more customers branch out into testing other grains. If you want to see all our options and sizes in ceramic sanding belts please do! 

Can I Use Ceramic Abrasives on Wood?

The short answer is yes, but...

It is best used on wood when you need rapid wood removal as it will not develop smooth surfaces. It is only good for roughing out and quick material removal. A lot of our customers who use wood as their medium use our ceramic sanding discs in the 8' model with the cloth backing. You will not see the ceramic perform to the best of its abilities when used on wood.

Wood is also not hard enough to allow the ceramic to renew and resharpen its grains. Wood itself is not hard enough to allow you to take advantage of the life-extending friability feature of these abrasives.  

Can I Use Ceramic Belts for Knife Making?

Absolutely! Ceramics have been slowly being adopted and used in many trades and is growing to be a favorite among bladesmiths as they can get so much use out of one ceramic belt as it lasts so much longer than both aluminum oxide and zirconia and can handle exotic metals. We have a wide selection depending on your personal knifemaking tools setup, but our  1' x 30' ceramic belts and 2' x 42' sanding belts are very popular in the knife maker community.

What Else Should I Know About Using Ceramics?

Abrasive ceramics are best used to grind and cut away other softer material. It's hardness and resistance to wear are unparalleled. That hardness is considered to be necessary so that the abrasive does not shatter during the grinding process. The grain self-renews with micro-fractures. As you use the abrasive, it will break down into smaller razor-sharp pieces multiple times over before it finally dulls. 

Although ceramic can be used for roughing out wood, it does perform best on hard metals. They are commonly used in deburring, deflashing, descaling, stripping, fast cutting, intermediate cutting, aggressive material removal, grinding, and ball milling to name a few. 

Benefits of Ceramic Abrasives

Long-lasting - can last up to 6x longer than other abrasive grain types

Friable abrasive - self-sharpening to continue working with consistent grinding and cutting

Low-pressure application - does not require the operator to exert as much pressure as other abrasives due to unique sharpness and hardness of the grains

Low temperature - generates much lower heat than the majority of the alternatives.

Is the Cost of Ceramic Worth It?

The cost of ceramic is generally at least 50% higher than most other abrasive grains. However, it will deliver between two and four times the performance over aluminum oxide or zirconia. When you are deciding on which abrasive is right for it is important to separate the price and the cost. The price may be higher with ceramic abrasives, but the total cost of the job (product + time + labor) will be substantially less.  

Another factor to consider is the long life of the ceramic abrasives. They generally last up to 6 times longer than their alternatives, meaning you won't need to buy replacements nearly as often.

What Grits do Ceramic Abrasives Come In?

Ceramic, like zirconia, comes in the coarser grits from as low as 24 to as high as 120. Ceramic is meant, as mentioned earlier, to remove the softer material and is only available in the coarser grains. 

What Types of Products Can I Get Ceramic In?

As ceramic is being adopted more and more as a superior abrasive by more people, it is being implement in more abrasive products. Ceramic can be found in pressure-sensitive adhesive discs (PSA), quick change discs,  sanding belts in a variety of sizes, resin fiber discs, and ceramic flap discs.  We are continually adding more ceramic-based abrasives to our line of products to keep up with all of our customers' needs.

Still Don't Know if you Should Use Ceramic Abrasives?

If you are unsure if ceramics are right for you, please do not hesitate to reach out to us. We know how difficult it can be when a few products may work for you and we're here to help guide you as best we can. Please feel free to reach out to one of our experts at Empire Abrasives, 1-800-816-. Whether you are experienced or a novice -- we are always happy to lend a helping hand. 

For more information, please visit Quartz Sand Proppant.