Vermiculite bricks are a service item, they withstand extraordinary temperatures and will protect your stove but are susceptible to damage and will eventually perish.
These vermiculite bricks line the fire chamber and protect the steel body from the heat produced by the fire.
Vermiculite bricks are a service item, they withstand extraordinary temperatures and will protect your stove but are susceptible to damage and will eventually perish.
They are fitted to the stove for insulation purposes, allowing your stove to burn efficently but also acting as a heat barrier and preventing the flame from reaching the steel stove walls.
A hairline crack in the brick will not damage your stove.
Replace the brick if;
It is advisable not to light your stove if the steel is visible. If your throat plate brick has fallen down, don’t use your stove as it will distort the metal throat plate, that holds the throat plate brick in place.
If you have any of the Stock Cube family of stoves or the Penguin 7 or 78 series, they have vermiculite bricks on the base of the stove. The same advise applies to these bricks. These are all wood only stoves, so smokeless fuels should NOT be burnt in them. We advise that you retain a layer of wood ash, approx. 2 cm deep on top of the base bricks. Wood ash acts as an insulator, it will protect your bricks. Occasionally you may notice that wood ash can “cake” on top of these bricks, this may be to do with moisture in the fuel. If you are removing this for an annual service take care that you do not damage the brick as you do it. Scraping and poking the bricks can damage them.
We have a few tips on how you can make your bricks last longer:
Vermiculite bricks are cut from a pressed board. They is common misunderstanding that they are fired ceramic brick or a quarried stone. This is not true. Vermiculite is a naturally occurring mineral formed into board and then cut into shapes. Not only does it work hard during its lifetime but when you have finished with it you can put it on your garden and it will degrade in to the soil. It an aluminium-iron-magnesium silicate.
Cracks are caused by impact or vibration, often simply a log/solid fuel thrown in a little roughly or the door squeezed shut on an oversized log. Crumbling on the edges or corners is a sign that the vermiculite is beginning to degrade and is ready to be replaced. How long it lasts will depend on how much the stove is used, under average seasonal evening usage this will usually be years.
Pinking; if the bricks change to a noticeable pink shade, this is sign that the stove has been over-fired, or burnt at excessive temperatures for a prolonged period of time.
When your fire bricks need replacing, we recommend buying fire bricks in sets for the following reaons:
Bricks are available on their own, should you wish to only purchase a single replacement brick.