Tile hardness; understanding the Mohs scale.

The Mohs scale of mineral hardness is a qualitative scale that characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material.

It was created in 1812 by the German geologist and mineralogist Friedrich Mohs.

A common requirement in our industry is to find out whether a tile is real porcelain or ceramic. You can use commercially available professional testing kits like the set depicted above or do a Mohs test yourself using commonly available materials you can find around the house or office.

Hardness of some common items on the Mohs scale.

2-2,5    Fingernail
2,5-3    Gold or silver jewelry
3-3,5    Copper coin
4-5       Iron
5-6       B2b ceramic tile
5,5       Steel knife blade
6-7       Glass
6,5       Steel nail
7          B1a porcelain tile
7+        Hardened steel file
8,5       Masonry drill bit 
9          Quartz crystal
10        Diamond

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How to test tile hardness in 5 steps.

1.    Find a clean surface on the tile to be tested. This is the 'unknown'.

2.  Try to scratch this surface with the point of an object of known hardness, by pressing it firmly into and across your test specimen. For example, you could try to scratch the surface with the point on a crystal of quartz (hardness of 9), the tip of a steel file (hardness about 7), the point of a piece of glass (about 6), the edge of a copper coin (3), or a fingernail (2.5). If your 'point' is harder than the test specimen, you should feel it bite into the sample.

3.    Blow or wipe off any dust. Examine the sample. Is there an etched line? Use your fingernail to feel for a scratch, since sometimes a soft material will leave a mark that looks like a scratch. If the sample is scratched, then it is softer than or equal in hardness to your test material. If the unknown was not scratched, it is harder than your tester.

4.    Now repeat the test, using a sharp surface of the known material and a fresh surface of the unknown.

5.     Most people don't carry around examples of all ten levels of the Mohs hardness scale, but you probably have a couple of 'points' in your possession. If you can, test your specimen against other points to get a good idea of its hardness. For example, if you can't scratch it with a copper coin, you know its hardness is between 3 and 6. If you scratch your specimen with a piece of glass, you know its hardness is equal to or less than 6 or 7.

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Quick answers.
Tiles are 'vitrified' i.e. 'turned to glass'. Ceramic tile will be scratched by glass but not by a copper coin. Real porcelain can be scratched by quartz but not glass.  You can buy quartz online, from new age shops, gemstone centers and some garden nurseries. A piece like this is perfect.

Below is a quick reference chart of the Mohs scale with common item equivalents.

What flooring lasts the longest?

When a customer comes into your store and expresses a need for a long-lasting floor, what do you answer? 

The short answer is ceramic tiles. They'll outlast any synthetic floor, natural wood, reinforced concrete or even steel by thousands of years!

Synthetics eventually degrade due to UV radiation, natural wood dries out or rots, concrete crumbles in time due to chemical action and all steel eventually rusts. These products will easily outlast their guarantee period but only ceramics are forever. The reason being that ceramics are vitified, meaning turned to glass. Technically in our industry this means having a water absorption of less that 0,5%, effectively the definition of porcelain.

To illustrate this answer I'd like you to take a look at some mosaics recently discovered in the ancient city of Zeugma in Turkey. Mosaics are essentially small glazed tiles (tesscera). The mosaics date back to 2nd century BCE, in other words they are over 2200 years old and in almost perfect condition.


One of the most amazing artifacts in the area is a collection of mosaics. Mosaics adorned the houses of wealthy residents that lived here thousands of years ago. Excavations at Zeugma started in 2007 and continue to this day.



The rising waters of the massive Birecik Dam on the Euphrates River brought about an emergency effort to salvage the artifacts left behind by the Roman civilization that once prospered here.

As the flood waters rose higher and higher, there was a lot of pressure to excavate the city. The image above shows the floodwaters rising over a mosaic floor. Today, 25% of the ancient town’s western bank is submerged 200-feet underwater and the eastern bank of the city is completely underwater. Still, there remains so much to be uncovered and learned in Zeugma.

It just goes to show, if you want a floor that will last more than a lifetime there's really only one choice... ceramic tile.

All the best from KREM tiles and the Link International team.

How to advise customers to find a tiler.

How often has a customer been in your store and having selected tiles for a project then asked you, "Can you recommend a good tiler?" Now it may be that you work for a large retailer and you have a ready-list of "recommended tilers" that you can hand the customer but even if you do, you should do more than hand over the list, you should advise your customer. Because the recommended tilers are separate, independent  companies, you can never be absolutely assured that they will do a perfect job this time around. It's important that the customer take responsibility for appointing a tiler and not you. If anything goes wrong you don't want to be held accountable for something completely beyond your control. Remember the vast majority of tiling failures are due to improper installation not product defects.

So what do you say? Here are five points to mention to your customer.

1. Get other referrals. Not all projects are the same, ideally get referrals from friends, family or colleagues who have had similar projects successfully completed. Ask referees whether the tiler was professional, how was their communication? If there were delays were these adequately explained? Finally ask the all important, 'Would you hire that tiler again?' Now check other references from the tiler who should be happy to provide these.

2. When you meet with a prospective tiler consider whether they look and act professionally. What is your first impression? Now ask them to quote. It's almost impossible to quote accurately without a site visit so plan for this.

3. Get quotes from at least three tilers. Make sure the quotes include labour, equipment hire if any, materials and an estimate of how long the project will take. The purpose of this is not to find the cheapest quote but to evaluate whether the quotes are 'in the ballpark'. If one quote is vastly more or less than the others, be suspicious.

4. This point stands alone because it is so important: Get it in writing! This contract is really your only come-back if something does go wrong.

5. Lastly find out about maintenance and care from the tiler. Get this in writing too. Some installations will require special treatment for days or weeks after installation.

Good luck with advising your customers and naturally improving your own professional standing.

All the best from KREM tiles and the Link International team.