Black Brick Slips

What Makes a Brick Slip Black?

So in terms of brick slips, a simple answer is that the bricks that these slips are cut from are either black themselves, or have black applications on them meaning the faces we cut off to use as tiles are the same.

Primarily the way bricks come to be completely black is based on the mineral composition of the clay used. Black bricks will start from clay with low iron content, meaning the redness you may associate with brick does not develop. This then needs to be enhanced by other additives such as charcoal, manganese dioxide or other carbon rich minerals, which are added in production.

The other aspect is the firing temperature of the bricks- they are fired at high temperatures, but also with low oxygen levels present to keep darker aspects in the process rather than have minerals reacting with the oxygen.

As we've come to understand more about firing bricks across the last century, we are able to manipulate the mineral content, firing length and temperature to get specific outcomes in colour, pattern and texture. However, brick is still crafted from natural clay so natural variation is always present.

How Are They Made?

Our black brick slips are cut from full bricks, or pre-moulded. This means that a 'stock brick' i.e one pushed into a cuboid mould will have the character, specifically creasing and imperfect cuboid shape, created by that amount of clay being pressed. Once the brick is fired we can then cut each side off the brick to create 2 brick slips.

 Our contemporary range is a little different. Because they are meant to be perfectly sharp edged, they are simply extruded into the shape of a brick slip already, this economises the amount of clay and the amount of energy used to fire them. They are engobed with their colour to provide a baked in consistent shade.

How Are They Different From Each Other?

The temperature of firing, oxygen levels, length of firing and type/quantity of minerals present mean that there is a variation in colour between each blend, and the slips within each blend too. Each brick type is made to satisfy a different colour palette, and they aren't all completely black- or even black brick beneath the surface.

Things To Be Aware of With Black Brick Slips

True black is a difficult achievement with brick, most colours are often more likely to be described as anthracite.

It's also important to note that when wet they will appear a little darker.

With a light colour the mortar makes a much larger impact than on darker shades, grey mortar often helps the black brick slips blend together- it's even possible to use a mortar dye to darken the grey mortar.

See below the effect that the different mortar colours can have on our black brick slips.