Difference Between Open and Closed Coat Abrasives

There is no "one size fits all" approach when it comes to abrasives. It comes in two primary forms of coating in addition to a range of sizes and types of grain (grit).

The term "coating" describes the degree to which an abrasive, such as ceramic or aluminum oxide, is applied to a product. We'll discuss the differences between open-coat and closed-coat abrasives as well as their appropriate uses in this blog. Selecting the appropriate one for your task helps prolong the life of your abrasives and contribute to a superior finish.

OPEN-COAT ABRASIVES

About 50–70% of the surface is covered by the abrasive grains when using open-coat abrasives. Although it might seem sensible to use as much abrasive grit as the surface will allow, leaving more excellent space between the grains might actually help your abrasive last longer.

An open coat decreases the possibility of sanding residue getting trapped between the grains by allowing more of it to flake off as you work with the abrasive. The running sander's action will typically remove any material that becomes stuck. Still, if the debris is too resistant, it can be readily removed using a cleaning stick or compressed air. Additionally, the open area promotes airflow, which lowers the abrasive temperature and keeps the wood resins and finishes from cracking in the heat.

It's possible to find semi-open goods when looking for open-coat abrasives. 30% grit reduction abrasives are referred to as semi-open coats. It still cuts less aggressively than closed-coat abrasives, although having a little bit greater cutting power than open-coat surfaces.

Softwoods like cedar, pine, fir, and spruce, as well as softer metals like brass, zinc, and aluminum, are commonly worked using open-coat abrasives. It performs well in rougher sanding and polishing as well, but it is not appropriate for finer, more even polishing tasks due to grit coverage gaps. 

The majority of abrasive grains are offered with open coatings; nevertheless, aluminum oxide abrasives are typically the only ones with open coating. If you're a woodworker or searching for a general abrasive to use on home projects, we generally advise using open-coat aluminum oxide solutions. Apart from those two categories, we usually suggest ceramic abrasives, particularly for people who create knives.

Since aluminum oxide belts are less expensive, knife makers frequently purchase them, even though the wood used to produce knives is either naturally hard (cocobolo, African blackwood, desert ironwood, etc.) or stabilized to be more challenging. In these situations, utilizing closed-coat ceramic abrasives will yield better results. 

CLOSED-COAT ABRASIVES

Closed-coat abrasives are more suited for hand sanding or working with more complicated wood and metal surfaces because 90 to 95% of their surface is coated in an abrasive substance. Closed coats have fewer spaces between the grains, which results in a smoother finish and more aggressive cutting because of the increased grit-to-surface ratio.

When working with tougher woods, this kind of abrasive is perfect since the coarser sanding process produces more significant bits that won't get caught between the grains. In other words, since the abrasive will not load as much, there is less need for more gap between grains.

Moreover, closed-coat abrasives are advised for:

• Grinding heavy metals requires the highest possible grain-cutting capacity. 
• Finishing products, such as sealers and lacquers, since they offer a higher-quality finish and a more consistent scratch pattern.

For softer materials, there are better options than closed-coat abrasives since the little gaps between the grain will fill up with sanding swarf (debris) very fast. The grit will eventually be covered entirely by a swarf, and an overloaded abrasive may end up scorching both the workpiece and your belt. Instead, use open-coat abrasives for these applications.

Making the appropriate coat choice for your sanding application will enable you to achieve the most significant outcomes most effectively. Benchmark Abrasives takes pride in manufacturing high-quality open and closed-coat abrasives for a variety of uses, including specialized and industrial applications, as well as individual woodworking and knife-making tasks.