Learn about Porcelain

Scratch Resistance MOHS Rating (Method Of Hardness Scale)

Scratch resistance of glazes is measured by scatching the glaze with a mineral of known hardness. Hardness of minerals is classified by MOH's Scale which lists 10 minerals according to their hardness. The higher the number the harder the glaze.

The scale is as follows:
1.  Talc
2.  Gypsum
3.  Calcite
4.  Flourite
5.  Apatite
6.  Microline
7.  Quartz
8.  Topaz
9.  Corundum
10.  Diamond
SHADE VARIATIONS - Due to the tremendous gains in technology in the ceramic tile industry over the past several years, manufacturers have been able to create looks that are truer to natural stone than ever before. These technological gains have been very positive for us all by creating new and innovative looks. They have also caused some difficulty since selling these types of tile takes a little more education than in days of old. In order to try to make things clearer and easier we have taken some information from the CTDA (Ceramic Tile Distributors Association) to clarify the situation with regards to shading.

The color shade and pattern of all tile varies to some degree from piece to piece and from production run to production run. In some tiles these are very slight (almost not noticeable) and in others they are very extreme (might look like different color tiles in the same box). Since this wide of a variety exists in shading today it is important for you to be educated about the tile you are selling and for you to educate your customer. Since our material is typically mid-high end products, shading tends to play a larger factor than in the lower end material.

We have added these symbols to our images which denotes one of the above levels. Since we have found that each person's interpretation of the above information is different, you must use this as a loose guide. Also, within a series by the same manufacturer the variation level may change with lighter colors having less variation and darker ones showing more. When in doubt have your customer approve a box from the current shade.
Differences among pieces from the same production run are minimal.
Clearly distinguishable differences in texture and/or pattern within similar colors.
While the colors present on a single piece of tile will be indicative of the colors to be expected on the other tiles, the amount of colors on each piece may vary significantly.
This tile resembles natural stone and may have extreme variations within a range of different colors. One tile can have totally different colors that are not present in others.
PEI Rating (Porcelain Enamel Institute)

This test is designed to measure the resistance of glazed tile to visible surface abrasion. Commonly referred to as "abrasion resistance" or "wear rating" this is the most widely asked for rating. Some tile surfaces will not scratch or scuff even under the heaviest industrial traffic while others are suitable only for areas of light residential traffic. Abrasion resistance in not a factor when selecting wall tiles so you will not find a rating on these. In brief, this test is conducted using water, abrasive grain, and steel bearings as the abrading method. The steel bearings (similar to ball bearings) are rotated on the surface of the tile with a machine and the tile is examined after pre-specified amounts of revolutions (150, 300, 450, 600, 750, 900, 1200, 1500, 2100, 12,000). The amount of revolutions it takes show an apparent visual difference in glaze or color will determine the tiles PEI rating.

These ratings are as follows:
CLASS 0  (100 revolutions) Suitable for walls only.
CLASS 1  (150 revolutions) Recommended for walls only.
CLASS 2  (600 revolutions) Suitable for wall use and floor use in residential areas where abrasive traffic is minimal, such as a bathroom.
CLASS 3  (750 – 1500 revolutions) Suitable for most all residential areas with normal traffic.
CLASS 4  (2100 – 12,000 revolutions or greater) Suitable for all residential and medium commercial applications (i.e. – offices, restaurants, hotel rooms, etc.)
CLASS 5  (12,000 revolutions and passes staining test) Suitable for heavy duty residential or commercial traffic.
WATER ABSORPTION (Frost Resistance)  
This test is done to determine the amount of water a tile will absorb and therefore its resistance to cracking in freezing conditions. We recommend a frost proof (FP) rating for outdoor use in climates prone to any freezing temperatures.

The water absorption rating is determined by how much water the tile absorbs although other factors and tests are also utilized to determine the frost rating.

As a general rule the scale is as follows:
(FP) Frost Proof  less than .5% absorption (Impervious tile) (FR).
Frost Resistant  typically .5 to 3.0% absorption (Vitreous tile) (NR).
Not resistant  manufacturer makes no claims as to the tiles resistance to freezing.
(NA) No information available  manufacturer has not conducted this test.
NOTES:  It should be added that proper installation is vital to any outdoor installation in which frost resistance or frost proof circumstances are trying to be achieved. Tile rated frost proof (FP) but not installed properly can still be prone to cracking. Be sure to use proper materials and technique in these situations.


In 2012, the American National Standards Institute updated their ANSI 137.1 standard to change the measurement system for tile slip resistance to DCOF, or Dynamic Coefficient of Friction. The new test measured the amount of force required to keep an object in motion as it slides over a tile. This new test better reflected real life situations where a person slips on wet tile. The new test is called the DCOF Acutest.

In addition to mandating the switch from SCOF to DCOF, the standard now requires a minimum wet DCOF AcuTest value of 0.42 for ceramic tiles for level interior spaces expected to be walked upon when wet..  According to the ANSI A137.1–2012 standard, ceramic tiles selected for level interior spaces expected to be walked upon when wet must have a minimum wet DCOF AcuTest value of 0.42. Tiles with a lower value, Polished tiles generally fall into this category, are not necessarily restricted to dry areas only, but rather are restricted to applications where they are kept dry when walked upon. In the case of residential bathrooms, the common use of bathmats can accomplish this. Similarly, in entranceways, the use of entrance mats can accomplish the same.  Of course a DCOF greater than .42 has an even higher slip resistance but may have a greater maintenance factor.

The Dynamic Coefficient of Friction (DCOF) test referenced in ANSI A137.1-2012 (Section 6.2) stipulates the use of a factory calibrated and validated, portable testing apparatus called the BOT-3000 Digital Tribometer, a self-propelled device that uses various sensor materials. The BOT 3000 is a portable machine which means that it could be used in a laboratory or in the field for testing Dynamic Coefficient of Friction (DCOF). The BOT 3000 is a type of Tribometer which measures the parameters such as frictional forces, coefficient of friction and the effects of lubrication. ANSI A137.1- 2012 has established that a Wet DCOF of .42 or greater for level interior spaces and if a ramp the requirement is greater than .42