Why is the glass in my woodburning stove door dirty?

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Dirty Glass

There can be three types of deposit causing dirty stove glass.

Dirt – Usually white smears. This is just deposits of wood ash and needs to be cleaned to improve the appearance of the fire.

Tar – An oily type of film – when minor, becoming brown treacle colour and even as black as road tar and impenetrable to light. This is as a result of the fire not being hot enough to cause complete combustion. Deposits can build up in the chimney and a chimney fire can easily result. This can be avoided by adopting two approaches; using dry fuel (<20% moisture content) and changing how the fire is operated. It is important to avoid over fuelling the fire for example letting the fire run very low and filling the firebox. Operating the stove at minimum output, with the top control closed will also cause this. A good rule of thumb is to refuel with no more than twice the weight of fuel which is left in the firebox. So if the fire is nearly out then add only a little fuel then let this burn properly before adding more fuel. This prevents the new fuel from overcooling the fire and causing it to burn in a sooty manner.

Sooting – A dusty, powder-like residue. This again is as a result of the fire burning incorrectly. The temperature of the fire is too low for the fuel to be properly burnt. Often this is accompanied by tar – but not always. If you are to use waste wood such as planks or MDF then the fuel will often produce too much flame in the early stages of operation after refuelling. This would then overwhelm the ability of the fire to burn the carbon in the flames, even if the fire is hot. There will then be sooting of the fire in the cold regions of the stove, usually the glass and around the door frame.

Cleaning the glass – There are two products available from Corinium Stoves that will clean the glass in your stove door effectively. These are the Stovax Glass Cleaning Gel and the Vitcas Stove Glass Cleaner spray (available from our showroom).

Other than these two products, you can clean the glass using a damp cloth dipped into the bed of ash at the bottom of your stove. The acid in the ash helps to clean any dirty smears.

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The Difference Between Single Wall and Twin Wall Flue

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The Difference Between Single Wall and Twin Wall Flue

Single wall flue pipe may also be referred to as single skin, vitreous enamel or connecting flue pipe.

Twin wall flue pipe may also be referred to as prefabricated flue pipe, factory made metal chimneys and double skin flue pipe.

Material

Single wall flue pipe is generally manufactured from steel and coated with enamel to provide a smooth internal and external finish. However it can also be manufactured using stainless steel with no enamel coating. The term “single wall” refers to the fact that there is only one layer of steel and no insulation.

Twin wall flue pipe is manufactured from stainless steel, usually of 316 grade quality. It is made up of two steel walls, which are kept separate by a layer of high grade insulation.

Finish

Single wall flue pipe is usually provided in either a matt black or gloss black finish, but can be sprayed to suit using high temperature paint.

Twin wall flue pipe is usually provided in a stainless steel finish, but can be powder coated in black or ivory to suit your preference. Powder coating is used rather than spray paint as it is more durable; twin wall flue achieves higher temperatures due to the layer of insulation.

Usage

Generally both single and twin wall flue can be used with gas, solid fuel and oil – but do check the specific product you intend to purchase.

Installation

Single wall flue pipe is designed to connect to the top or rear outlet of a stove and essentially act as the connecting piece between the stove and the main flue system. This flue system may be flexible flue liner that is installed into a masonry chimney, or it may be a twin wall flue system.

A twin wall flue system is used when a stove is fitted into a property where no masonry chimney exists. It can run internally or externally and therefore doesn’t just comprise of lengths of flue pipe that we have been discussing in this article.

You cannot use single wall flue pipe in place of twin wall flue pipe. Single wall flue pipe is not insulated and therefore loses a lot of heat. The layer of insulation in twin wall flue keeps the flue gases warmer, allowing the flue to perform correctly and efficiently, whilst also reducing the build up of condensates within the flue system.  Single wall flue pipe is also not designed to be fitted through walls, ceilings and roofs as with twin wall flue pipe. The insulation in twin wall flue allows a clearance of only 50-65mm (depending on the specific flue system) to combustible materials, whereas single wall flue needs to be three times the diameter of the pipe away from combustible materials.