As it has a closed chamber, the Harrison utilises four methods of heat transference: radiation, convection, conduction and direct heat. These ovens don’t need electricity or gas and can work with any type of charcoal and many types of wood.
The temperature is controlled by an exterior handle that increases or decreases airflow to the solid-fuel chamber from the lower vent. The immediate impact that has on the embers - and therefore the temperature - is exhilarating to see. As the top vent draws the air through the oven’s closed chamber the temperature will build.
From a cold start it takes roughly 30 minutes to get up to cooking temperatures of 250–300°C. After another 15 minutes or so, the walls of the chamber become ‘charged’, which means the Harrison is now using radiant heat, which can be retained for a whole service, if required.
The Harrison is quick, easy and clean to light using additive-free firelighters. The choice of wood or wood chips used will have a subtle but distinctive impact on flavour, and the same is true of the choice of charcoal, too.
Charcoal and wood are organic, natural, non-toxic and more cost-effective than conventional-fuel ovens. The average consumption is 3kg coal for a full food service (depending on the menu/covers etc.). The Harrison’s chamber has been designed to retain heat, which means it cooks 35% faster than an open charcoal grill and uses 40% less coal.
Charcoal is best for slow cooking, high temperature cooking and baking. Harrison recommend using 100% sustainable, finest quality, restaurant-grade charcoal.
Briquettes are blocks of compressed charcoal, which can be used across baking, high and ultra-high temperature cooking, as they tend to last longer periods of sustained, consistent temperature cooking. They are harder to light than standard charcoal.
Untreated, dry wood works well and can add subtle smoky notes to your cooking. Use for hot smoking, baking breads and pizzas. Try different kinds of wood, or wood soaked in aromatic liquids for creative flavour variations.
Wood chips are great for hot smoking and are available in several varieties, such as oak and beech. To add an infused flavour, soak chips in a liquid flavour of your choice, then place in the oven to add smoky notes of your chosen wood or liquid to your cooking.
Wood dust smoulders and burns cool producing lots of smoke with very little heat. Use in a cold-smoke generator to turn your Harrison Oven into the perfect cold smoker.
Inside the Harrison
The metal shelves inside the oven are as strong as the rest of the Harrison and hold their own weight when pulled out. They can be positioned at various heights to maximise the Harrison’s range of temperature capabilities and be cooked on directly for the most searing temperatures. Its exterior roof shares some of the heat of the inside and can be used for resting, warming or sauces.
When using your Harrison Oven inside, it should be positioned under an extractor hood. Due to the nature of burning solid fuels, the minimum extraction rate will always be 750m3/hour or higher, therefore a standard, domestic extractor hood may not be sufficient.
Before installing your oven, advice should be sought from an extraction expert as to your exact needs. The extractor unit must vent outside and not recycle the air back into the room. The exact rate of extraction required will vary due to the dimensions of the room, natural ventilation and airflow and any other equipment being used in the vicinity.
As with any solid-fuel burning device, a carbon monoxide monitor should always be used in conjunction with an extraction hood.
Every Harrison oven is designed to be easy for the user to keep in top condition. All oven parts, from the handles to hinges and catches are screwed in place, not welded, which allows simple adjustment with an allen key or screwdriver if required, but also means that if any part becomes damaged it is easy to be replaced without the need of a engineer call out.
To keep the oven door performing to its maximum, the hinge pin can easily be removed and cleaned with warm soapy water. This will keep it free from grease and ash and allow the door to operate smoothly.
The bottom vent slide should also be removed frequently and cleaned. This is a simple process and will keep temperature control intuitive and free of resistance.
The outside of the oven can be cleaned with warm water, when cool and the oven’s inner chambers and cooking racks can be cleaned with a wire brush if required.
If the oven is being used daily, charcoal racks should be flipped every few weeks to extend their life.