QUESTION

Staining Granite - Our kitchen, scullery and laundry room has beech colour granite tops which are fairly light in colour. Sadly it is staining quite badly and the granite supplier said that it's the colour we chose but also we have to be careful with what we put on it. Every single home we go to does not have this problem and they put hot pots & pans directly on the granite.

We received a second opinion and they said that the initial sealing process was not done properly and hence the staining. No matter how many times you treat the granite tops it will stain. Water marks come and go but in a kitchen we use oil and various other ingredients for cooking. The oil marks are staining permanently.

I would be very grateful if I could get some advice as we are considering the legal route with the supplier.

Sadly there is no body for granite specialists. For approximately US$10,000 worth of granite in a kitchen, should we be experiencing these problems????

ANSWER

ANSWER - Chances are the stone that you have may be over-burden granite or a type of metamorphic stone called gneiss, which commonly is sold as granite.

Often these types of stones are very colorful with a lot of movement and desirable by the consumer.

Many of these stones are less stable than good quality granite so they are treated with a resin at the processing plant to provide more stability during transportation and fabricating.

Granite is an intrusive igneous rock composed of 25% to 35% quartz and over 50% potassium and sodium—rich feldspars, with about 20% minerals.

Granite and these other stones will vary in their physical properties depending on where it is mined relative to which part of the world, which quarry and which location within the quarry it was extracted.

There are physical properties standards for Granite per ASTM C615 for it to be considered standard grade granite.  The absorption of the granite must be between 0.02 and 0.40 percent, which makes it very stain resistant.  Granite is resistant to acidic material that will etch some stone surfaces leaving stains. Granite and other types of stone are very resistant to heat, but if it has been treated with a resin it may not be as resistant, but it is known to be resistant to heat with quality resins.

The resin coating on the slabs that have it can stain or smudge when subjected to certain materials or conditions.

If your stone slab is readily absorbing water and other liquids then it is high in absorption and likely not a true granite.

The only way to know for sure what you have and its physical properties is to test it, which could cost several thousand dollars.

You can apply sealers that will help make the stone more stain resistant, but they only work if material does not sit on the surface too long and that it is reapplied about every 6 months.

Good Luck!