Introduction
Sandpaper, the friendly name for a coated abrasive, is used by DIY enthusiasts and professional tradespeople alike. Although sandpaper has a wide range of applications, it is most typically used to prepare surfaces for painting, varnishing, or otherwise finishing. Even the best orbital sanders rely on having the correct sandpaper grit in order to perform at their best. For this reason, we decided to take a deep dive into the different types of sandpaper grit available and the grits required for each type of sanding task.
The name itself dates back to 13th century China where sand (Along with crushed shells and seeds) was bonded to paper using natural gum. In the united states, sandpaper was not commonplace until 1935, when sandpaper was patented by Isaac Fischer, Jr., of Springfield, Vermont.
While sandpaper is no longer made using grains of sand, the name has stuck and is now what we use to refer to a range of different backing materials covered in various types of abrasive particles. Regardless of the exact makeup, the requirement remains roughly the same; to effectively remove imperfections and prepare a surface for finishing while minimizing the required effort.
Table of Contents
1 – Why choosing the correct sandpaper is important
2 – What is sandpaper made of?
2.1.1 – backing material
2.1.2 – abrasive material
2.1.3 – other variables to consider
3 – Sandpaper Grit Rating standards
3.1 – Coated Abrasive Manufacturers Institute (CAMI)
3.2 – Federation of European Producers of Abrasives (FEPA)
7 – FAQ
Why is choosing the correct sandpaper important?
Sandpaper comes in many different forms; not only are there various backing materials and abrasive particles, but there are also multiple shapes of sandpaper for use with specific tools. There are also different standards for the size of the particles that make up the grit component of the sandpaper, and there are different levels of coverage.
All of these factors require careful consideration because using the wrong type of sandpaper will impact the sanding process. At best, this will make the work a lot harder than it needs to be and, at worst, could ruin the surface that you are sanding.
Although choosing the correct sandpaper may seem like a daunting task, it does not have to be and with the help of this guide, you can be fully informed on the various attributes of sandpaper, allowing you to make an informed decision on what type you need to purchase for your project.
What Is Sandpaper Made of?
There are several components that make up sandpaper including the backing material, the abrasive coating, and the adhesive used to secure both of these together.
Backing Material
There are different types of backing material used for sandpaper depending on its use. The most common material used is paper due to its relatively low cost of production but also its versatility. The quality of paper used will vary; for example, if the sandpaper has been produced for use with powered tools, such as the random orbital sander, it is generally higher in quality.
When the sandpaper has been designed for use with lubricant, a waterproof paper would be used in place of the standard backing material. A good example of this would be in the case of wet and dry sandpaper, designed for use in conjunction with water.
Cloth is also used as a backing material in some sandpapers. Although less common, it is an ideal backing material for cases where greater control and flexibility of movement are needed, which is often the case with intricate sanding work.
Abrasive Material
In order for sandpaper to be effective, it needs an abrasive material, in the form of tiny particles, securely attached to the backing paper. These abrasive particles effectively scrape away at the surface to which the sandpaper is being applied.
There are many different materials that can be used for this purpose, depending on the intended use of the sandpaper. We have listed the most common materials below.
- Garnet – A group of natural, silicate minerals ideally suited to woodworking projects. Garnet has a unique quality in that the particles will fracture during use. The result is a gradual reduction in the abrasiveness of the sandpaper which makes it ideal for finishing work but does have the disadvantage of reduced durability.
- Aluminum oxide – Suitable for a range of surfaces including wood, plastic, metal, and drywall. This is one of the most durable abrasives thanks to its chemical composition (A1203) forming a strong crystalline structure. Aluminum oxide is used by Norton Abrasives (One of the largest manufacturers in the US). Aluminum oxide is the primary component of Emery hence the name of the common abrasive used for metal sanding – emery cloth.
- Silicon carbide – The black, shard-shaped grains are harder and sharper than aluminum oxide and thus are the better choice for use with hard materials such as paint, plastic, metal, and hardwoods such as cherry. The downside to silicon carbide is its lack of durability and high cost of manufacture. This material is often used with wet and dry sandpaper as it can be used both with and without lubrication.
- Zirconia alumina – a composite ceramic material comprising a mixture of aluminum oxide and zirconia to form a stronger and more durable grit. Typically used on belts and discs for heavy-duty sanding.
- Glass – typically composed of quartz granules, glass sandpaper offers a low-cost alternative to other abrasive materials. Glass is less common for use in sandpaper due to its lack of durability although it is suitable for sanding timber, metal, and other materials.
Other variables to consider when selecting the correct sandpaper
In addition to the physical materials used with sandpaper, there are several other qualities that vary depending on the type of sandpaper and its intended use.
The density of Sand Paper Grit
Sandpaper comes in several different grit densities. The first one being closed-coat where the abrasive material or grit covers 100% of the surface. The alternative is open-coat sandpaper where the abrasive material covers only 50-70% of the backing material. The advantage with the latter option is that clogging is less likely to occur and thus it is the preferred choice when sanding wood or other soft materials.
Shape and Form of Sandpaper
There are many different ways in which you can apply sandpaper to the surface of your material. The most common form is manual sanding by hand, which is best suited to light or delicate sanding work. You can make this process slightly more comfortable and efficient by using a sanding block but either way, sandpaper in sheet form would be most suitable for this method of application.
The most common alternative to hand sanding is the use of a power tool such as an orbital sander, a belt sander, or a drum sander. Each sanding tool typically has its own requirement when it comes to the sandpaper form; for example, an orbital sander will typically require a disc, whereas a belt sanding uses a sanding belt. For anything other than manual sanding you should consult the manual that came with your power tool or use the model number to search online for the manual, in order to find the specifications of the sandpaper required for that particular tool.
Sandpaper Grit Rating and Standards
The grit rating of sandpaper is arguably the most important factor as it will dictate how much, or how little, the material is removed from the surface that you are sanding.
Before we get into the specifics of grit ratings, it is useful to understand how the rating system works, that way you can better understand what you are looking at when you see the various denominations on any given packet of sandpaper.
Although there are many different grit standards used throughout the world there are two common ones that you should be aware of.
Coated Abrasive Manufacturers Institute (CAMI)
The CAMI standard takes its name from the Coated Abrasive Manufacturers Institute, which has now become part of the Unified Abrasives Manufacturers Association. This standard is most commonly used in the US and is represented by a number ranging from 12 (extremely course) up to 1200 (Extremely fine). The CAMI standard generally allows for a greater range in the size of particles in each rating category making the grading system marginally less accurate but simpler to understand.
Federation of European Producers of Abrasives (FEPA)
The FEPA standard is used more widely throughout Europe and is denoted by the letter “P” followed by a number. The FEPA standard ranges from P12 (extremely course) up to P5000 (Extremely fine).
Both standards are similar in so much as they use a numbering system to represent the average size of the abrasive particles on the backing material of the sandpaper. Each standard has its own tolerance levels used when testing the average particle size. The testing itself is typically done using sieves with known opening sizes although FEPA also uses sedimentation to measure particle size distribution in micro grits.
Whilst the two systems of sandpaper grit are similar up to around the (p)240 mark, afterward, they start to differ more and more as the scale goes up.
We have compiled a simplified table of the most common sandpaper grits and their respective ratings from each standard – see below – which includes the rating number for FEPA and CAMI along with the broad category into which the rating falls. We have also included a note on the most common use-cases within each category.
There is also a more detailed document available which covers the sandpaper grading along with the equivalent particle sizes (In microns) – available for download here – abrasive grit rating guide for sandpaper (Original source).
Sandpaper Grit Chart
How to Use Sandpaper
Now that you know how to choose the right sandpaper for the job, you can well-informed decision about the type of sandpaper you need to purchase in order to complete your project efficiently and to a high enough standard.
The next step is understanding exactly how to use your sandpaper effectively, to produce the desired results.
Start with a coarse grade of sandpaper
The number one tip for any sanding project is to start with a coarse grade of sandpaper and work your way towards finer-grade sandpaper as the work progresses.
The course grade means a lower number regardless of whether you are using the CAMI or the FEPA grading system and will remove more material from the surface.
Start off on a small area of the material to make sure the sandpaper has the desired effect – using a sandpaper grade that is too coarse, especially if you are sanding a soft material such as pine, can damage the surface.
Once you are happy that you have the correct grit sandpaper, begin sanding the material in light, consistent movements. If you are sanding grained wood, be sure to move the sandpaper along the grain rather than against it. Whilst it may be tempting to press harder on the surface, you should instead use light but firm pressure, allowing the sandpaper itself to do the majority of the work.
If you are sanding a non-grained surface, then move the sandpaper in small circular motions.
When sanding a large, flat surface it may be beneficial to use a sanding block as this will allow you to keep consistent contact with the surface as well as taking the further strain out of the work.
However, if you are sanding an intricate surface then sanding by hand only will produce better results and allow you to move the sandpaper along the contours of the surface more easily.
On very large projects such as dining tables or hardwood floors, it is advisable to use a power sander.
As you begin removing the unwanted material from the surface being sanded, you can gradually move towards the finer grades of sandpaper. As you do this, you will gradually produce a smoother surface as a result of sanding. Starting off with coarse sandpaper, then moving to medium grit sandpaper before finally making use of fine-grit sandpaper will produce the best results.
Where to Buy Sandpaper
You can purchase sandpaper from any local hardware store, or if you prefer shopping online then Amazon is ideal; especially if you know exactly what grade of sandpaper you are looking for. Typically, you will find lower prices when shopping online, compared to shopping in a local store.
Click here to browse the full range of sandpapers stocked by Amazon.
Sandpaper Frequently Asked Questions
Hopefully, you now have a complete understanding of sandpaper in terms of how it is made, what grit ratings should be used for each type of DIY project, and also how to best apply sandpaper for the highest quality finish.
For everything not covered in the main article, we have included an FAQ that should answer any remaining questions that you have about sandpaper. If you have read through our article and find that your question has not been answered, please feel free to get in touch with us and ask your question. We will provide you with an answer and add it to our list of frequently asked questions.
how is sandpaper graded?
Sandpaper is typically graded using one of two coated abrasive standards – CAMI and FEPA. Each of these two grading systems has a scale of grit numbers ranging from low (course) to high (fine-grit sandpaper).
how does sandpaper work?
Sandpaper is made up of a backing material (Typically paper) and an abrasive material (Typically garnet, aluminum oxide, or silicon carbide which is effectively glued to the surface. As you rub the sandpaper over the material that you are sanding, the abrasive particles on the sandpaper will cut into the material, stripping a layer off the surface.
how to make sandpaper?
You can make your own sandpaper by sticking an abrasive substance to a surface such as paper or cloth. You can use a range of different readily available materials for the abrasive component including glass, aluminum oxide, and even sand.
Alternatively, you can also reuse used sandpaper discs from an orbital sander if you own one.
how to measure grits?
Sandpaper grit is actually measured in microns but for simplicity, the grit sizes are denoted using a fixed scale created by an abrasive standards organization – the most common ones being CAMI and FEPA. The measurements are carried out, most commonly, using a sieve with openings of a certain size – on the basis that any grits falling through the sieve must be no larger than the grid opening.
how to wet sand metal?
In order to remove scratches and imperfections from metal, you will need wet and dry sandpaper – this is typically made using either Silicon carbide or aluminum oxide. The crucial component when it comes to sandpaper for metal is that it should be waterproof. The reason being is that you need to apply water or another lubricant along with the sanding. If you would like to incorporate your power sander into the process, read our guide on how to wet sand with an orbital sander as there are certain safety requirements that you must take into consideration.
When sanding metal you should use a circular motion with the sandpaper for the best results.
how to sand wood by hand?
Sanding wood by hand is beneficial when you are sanding small surface areas. You should start of with a course grade of sandpaper. As you begin to work out any imperfections in the surface of the wood, or scraping off materials from the surface, you should gradually move to finer abrasive sandpapers.
what grit sandpaper for wood?
If you are planning to remove bumps or reshape the wood, then start off with P40 – P60 sandpaper (40 – 60 on the FEPA scale). If you are sanding a softwood such as Poplar, Redwood, Cedar or Pine then start off with a grit rating of P120.
As the wood becomes smooth and the imperfections have been removed from the surface, move gradually to finer-grade sandpapers, culminating with something in the region of 320 grit sandpaper or 400 grit sandpaper for finishing.
what is the finest sandpaper?
The highest grit sandpaper is 1200-grit but this is not typically used on home DIY projects. In practical terms, the highest grade of fine sandpaper you would need is around 800-grit to 1000 grit sandpaper which would be ideal for final sanding and also for use prior to and during polishing.
what is medium grit sandpaper?
Medium grit sandpaper would be anything ranging from 60-grit to 100 grit sandpaper. Anything lower than 60-grit would be considered course and 120 grit sandpaper upwards would be considered fine. Although the scale is open to interpretation, this is a safe estimation to go by.
what is the coarsest sandpaper?
The coarsest sandpaper is 12-grit, although this would not typically be used for DIY projects and is in fact hard to find. The lowest grade, and coarsest, sandpaper typically used would be 24-grit which is ideal for use with drum sanders when carrying out initial sanding efforts on hardwood flooring.
what grit sandpaper for drywall?
Because drywall has a fairly loose makeup, you do not need anything too course in order to sand down its surface. Typically, a grit rating of around 240-grit would be suitable for sanding drywall.