One of the questions we are most frequently asked by the owners of new stoves is how to clean the glass.
There’s an essential preamble that we would normally give before discussing the solution to dirty glass, regarding cause, effect & avoidance, but in the interests of brevity, I’ll treat it here as a post-amble and get on with answering the question first (more info at the foot of the page).
Essentially, there are two conditions that can occlude the glass of a stove’s door. Browning-up, whether just in the corners or across the whole pane, is due to gases released during combustion condensing on the glass. These can be removed.
However, the cheapest - and very effective – means of cleaning the glass is with damp newspaper, or a rag, dipped in the ashes, which are mildly acidic.
Even a dry wipe with a sheet of newspaper can remove surface marks from the glass, especially a thin grey film which can sometimes occur; dampening it will shift darker stains, and by dipping it in the ashes, and applying a little elbow action, it is usually possible to make the glass pristine in a matter of seconds.
The spray cleaner we sell does essentially the same job: you spray it directly onto the glass and wipe it off. It’s slightly faster and less messy. However, it is worth being aware that, because it is quite corrosive, it can mark a porous hearth if splashes land on it, and we have learnt the hard way that if it leaches behind the door rope on stoves with black-painted glass, like our showroom Contura 510G, it is strong enough to dissolve the glass paint and possibly even the rope glue!
One way of avoiding chemicals at all is the dry wiper we also sell, which is similar to a Brillo pad, but designed to be used on stove glass without scratching it.
It is possible to inadvertently bake creosote onto the glass of your stove, and it requires an awful lot of elbow grease to shift the traditional way. In these circumstances, we recommend a gel cleaner, which is like an oven cleaner: highly corrosive but extremely effective. You apply it to the glass, leave it a few minutes, then wipe it off. You’ll want to wear gloves, unless you have surplus layers of skin to sacrifice, but your glass will shine like crystal afterwards.
The second type of marking you can get on the glass is a whitish kind of bloom, usually resulting from over-heating, the burning of treated wood or rubbish in the stove, or, unusually, because of defects in the ceramic glass. This can usually not be removed, although it’s always worth having a go, and while it represents no impediment to using the stove, it can be irksome if you’re used to the glass being essentially invisible during stove use. The only fix in this case is to replace the glass.
Post-amble: Browning-up of the glass in a stove occurs when the volatile gases released by wood during combustion fail to ignite and condense on the first cool surface they hit. This is often the glass, but if you have tar forming on the glass, it is probably happening elsewhere in the stove too, as well as in the chimney. The primary culprit is damp wood, which depresses temperatures in the combustion chamber, as well as adding water vapour to the other gases. Wood is far more likely to smoulder if it is not properly seasoned, and the burning of damp wood will always produce browning up of the glass, no matter how good the stove is.
Too little oxygen in the combustion chamber can also produce incomplete combustion; it’s never a good idea to close the air supply down on a fresh log or even before wood has been reduced to charcoal; in these circumstances you will almost always get some grubbing-up of the glass.
Conversely, an excess of air can duplicate the effect, although not usually as badly, mostly because a stove run with the air controls wide open can compromise the effectiveness of its airwash system, but also because the quantity of inert nitrogen in the air mix can actually depress the combustion temperature by absorbing heat from the secondary gases.
Most modern stoves have some kind of airwash system, of varying efficacy. In our experience, Clearview’s is the most effective, and we very rarely have to clean the glass at all on our three showroom Clearviews or on our stoves at home. It helps that the door is also double-glazed, an innovation now also being introduced on Chilli Penguin stoves, as this provides an extra layer of ‘insulation’ that serves not only to help keep the glass clean but to maintain a high combustion-chamber temperature. However, all of our stoves, used with properly-seasoned logs, should burn extremely cleanly and only require minimal attention to the glass, and we have been particularly impressed with the latest generation of Chesney’s wood-burning stoves in this regard.