Traditionally the term Marble was used by stone masons to describe any stone that would take a polished finish. From a geological point of view however, Marble is defined as Limestone which has been subjected to thermal metamorphism. This process of metamorphism leads to a dense, closed surface although some material may have slight open veining or surface pitting. Marble has been used for centuries due to the vast spectrum of beautiful shades and mineral veining. Some Marble tiles or slabs with particularly prominent veining may have a mesh backing applied to the rear of the tile, predominantly to reinforce the material during transport and cutting. It is also common practice for resin filler to be applied to voids and open veins either before or after processing. Marble is a very dense stone that readily lends itself to a polish but is also available in Honed and Tumbled finishes. Honed has a smooth non polished surface, edges are either straight or bevelled which gives a contemporary/classic look. Tumbled has a rounded antique finish sometimes leaving the surface more open and slightly textured. Easily dulled, stained and etched. Acid sensitive and porous.

Impregnating sealer is required. Surface sealing is recommended, and regular maintenance is necessary

Travertine begins as a calcareous dispersion which is then deposited by hot mineral springs. The result of this method of formation is a honey-combed structure which when finished has visible surface pitting and voids. Travertine generally comes in either ‘cross-cut’ or ‘vein-cut’ formats. Vein-cut tiles are cut so that the surface plane of the tile runs parallel to the long veins present, cross-cut tiles are cut perpendicular to these veins. Once tiles are cut, they are then either filled with a colour matched resin or left unfilled. Generally, the voids are only left unfilled in Tumbled, Brushed or Split face finishes, these voids are filled during the grouting process. Although filling of the voids gives a smoother surface, through general usage, some small areas of fill may dislodge, or previously unexposed holes may become visible. This is not unusual, and the holes should be re-filled with a suitable resin or grout. Acid sensitive and porous.

Impregnating sealer is required. Surface sealing is recommended, and regular maintenance is necessary. In practice these stones require a base sealant to quell the porosity, followed by a liquid surface wax which provides a slight finish and forms an additional protective layer. Base sealants can be either solvent-based or water-based and the base sealant required differs depending on the density and finish of the material being sealed. Solvent-based and water-based sealant options should not be mixed.

A fine-grained metamorphic rock that is characterised by its ability to be split into broad sheets, Slate is a durable stone which presents a diverse range of colours and textures. Riven Slate has a naturally cleft surface and is rustic by its nature, with chips and chisel marks present on some surfaces and can be used both internally and externally. Some Riven Slate is ‘uncalibrated’ meaning it will vary in thickness both across individual tiles and from tile to tile. Honed slate is machined to create a smoother, more even surface. Not sensitive to acid and semi porous.

Slate is naturally less porous than many other stone. Depending on the chosen finish, an impregnating sealer can be used solely, or a liquid wax surface sealant can be added for surface protection. These sealants are resistant to wear and tear and also highly dirt and dust repellent. If the situation does not allow for use of a liquid surface wax, then a designated impregnator can be used to seal Riven Slate.

These are densely crystalline, metamorphic rocks that offer considerable shade variation, ranging from light cream/white to charcoal grey/black with many colours in between and often contain reflective crystals which glisten in the light. Highly textured.

Denser than limestone or sandstone but still needs impregnating and surface sealing.

The term Granite is generally used to refer to a large range of Igneous rocks originating from the slow crystallisation of molten magma cooling deep beneath the earth’s surface. Due to the nature of this material and the vast array of mineral crystals that serve to make up this stone, characteristics can vary greatly, and some may be acid sensitive, requires a penetrating sealer only.

A coarse-grained sedimentary rock formed by compressed sand deposited by water or wind. Sandstone is available in a Riven finish which is characterised by its granular, undulating surface, or a smoother Honed finish which varies in texture with some edge chipping. Sandstone is a hard (high quartz content) yet very porous stone that, if being sealed, requires thorough impregnation with suitable sealants. Not sensitive to acid.

A thorough application of base sealant is required to ensure that it is as protected as possible. If a matt or satin finish is required a topical sealant should be applied to the surface thereafter. If fixing externally, the material can either be left unsealed and allowed to weather naturally or sealed to offer protection.

Terracotta is a type of rustic ceramic made from natural clay which has been moulded and then kiln fired to bake the clay and produce rigid tiles. The clay is either moulded by hand to give a more rustic feel, or machine-moulded for a more consistent finish. All Terracotta tiles will be subject to edge chipping and variation which is part of the finished look of an authentic Terracotta floor. Terracotta when untreated is very porous and as such any unsealed tiles will look very different from your finished floor.

Two methods of sealing can be adopted; traditional oil and wax or the modern approach using synthetic sealers.

Traditionally, Terracotta tiles were sealed using a 50:50 mix of Boiled Linseed Oil & White Spirit, followed by a paste/beeswax treatment. Terracotta tiles are raw, exceptionally porous tiles, made from natural clays and so need to be thoroughly sealed. Terracotta tiles need to be clean and dry prior to applying the impregnating sealer, 1-2 more coats of the chosen base sealant should be applied. Depending on the desired finish and once the base sealant has dried a surface liquid wax can be applied across the surface.

Porcelain tiles are a type of ceramic with a very low absorbency. They are usually made from kaolin clays and fired at around 1,200°C, due to this high firing temperature and high density they are very hard wearing. There are three types of Porcelain tiles; full bodied, part bodied and polished. Full bodied is where the tile has no glaze so the colour/design is the same all the way through, if there was any wear or chips to the tile it would be very difficult to see. Part bodied is where the tile colour/design is at the surface of the tile, any chips or wear would expose the backing underneath. Polished porcelain has been manufactured with a glaze applied to the surface, very hard throughout but the glaze has the same characteristics as ceramic tiles.

Tiles referred to as Ceramic are generally fired at lower temperatures than Porcelains and usually colour glazed to give a matt or gloss finish. Unlike natural stone they do not require sealing.

Absorption rates vary widely:

• Porous bodied glazed ceramics with water absorption greater than 10%, only suitable for indoor use.
• Medium water absorption from 6 to 10%, for indoor use only
• Semi vitrified water absorption 3 to 6%, for indoor use only
• Vitrified water absorption 0.5 to 3%, frost resistant, suitable for external use but may benefit from sealing
• Fully vitrified water absorption below 0.5%, frost proof, suitable for external use.

Polished Limestone, Marble, Travertine and Honed Slate: These stones have lower porosity levels and so will not absorb as much sealant as other finishes, only require a penetrating seal.