From the Georgian Period forward, the majority of the London townhouses were heated by coal rather than wood. Thus, members of Society and visitors to the City “enjoyed” the ever-preent film of coal dust in the air. In the late 17th and early 18th Century, the fireplaces remained wood-burning elements within the households. These fireplaces were designed with wide chimneys and a brick hearth.
When coal came into use, a free-standing iron or steel basket was placed in the fireplace. These baskets usually had an iron fireback behind it. After 1750, these iron baskets occurred regularly in both country, as well as city, households. Quite often, down drafts drove smoke from these coal baskets into the rooms, and the heat escaped up the chimneys (i.e., the constant “smog” in London). A fireplace fireback is a heavy cast iron, sized in proportion to the fireplace and the fire, which is placed against the back wall of the fireplace. The metal is heated by the fire, and then that heat is radiated into the room. The thick iron keeps the heat which would otherwise be lost and returns it to the room. A fireback may increase the fire’s efficiency by as much as 50%. The thicker the fireback, the longer (and softer) the radiative effect. The fireback also protected the back of the fireplace from heat and flames.
Stove “grates” became popular in early to mid 18th centuries. These stove grates combined the coal basket, the fireback, and firedogs. The first fireplaces in Tudor homes consisted of a pair of fire dogs, which raised the ends of the burning logs to improve the burning efficiency. By the end of the 18th Century, the first fire baskets came into use, which helped to contain and manage the fire, improving efficiency.
From Russell Taylor at Building Conservation, we learn, “Chimneys and flues are subjected to intense heating and cooling cycles, condensation and aggressive chemical reactions caused by hot flue gases. Above the roof line the chimney stack is exposed to the full force of the weather. To withstand such conditions, maintenance and repairs need to be of the highest standard, and it is important that design elements of such significance are conserved properly. Yet works are often badly executed by unqualified contractors using inappropriate materials and ill-conceived methods. The result can be damaging to the character and fabric of the building, and may even be dangerous.
“Although flues have been in use since ancient times, many early domestic fires were open hearths where the smoke billowed around inside the building. The widespread adoption of flues in the late medieval period coincided with an increase in the use of brick, which is better able to withstand the temperature of a domestic fire than stone because it is a fired material. Even in stone building areas brick was often used for the chimneys and flues, particularly from the 19th century onwards.
“The earliest chimneys were large, crude structures serving a single fire, but as more fireplaces were required, chimneys became smaller and more efficient, combining several flues, each serving a separate fire.
“At first the usual domestic fuel was wood, but coal was used surprisingly early – in London from the mid-17th century and everywhere except rural areas by the mid-18th century. The change to coal resulted in smaller fireplaces as more heat is given off by a smaller quantity of fuel, and grates were required because coal, being denser than wood, will not burn unless there is an oxygen supply under it.
“In the 17th and 18th Centuries, when coal was the principal fuel used, grates were really simple baskets combining fire-dogs and fire-back in a single unit. Then came cast iron hob-grates and finally the various types of register grates based on principles established by Count Rumford in 1797. These grates had a narrow throat for more efficient flue draught, the fire was pushed forward to the front of the hearth and the sides were splayed to radiate heat more efficiently. Register grates became the standard from then on.
“By the 18th century most chimneys were built with 12″ flues, and this size was reduced still further following Count Rumford’s innovations. As a result the usual dimension for a brick flue came to be just 9 x 9″ (one brick by one brick) and the wall between the flues, the ‘withe’, was usually 4½” (half a brick). Brick dimensions often also govern the dimensions of quite elaborately shaped stacks so for any replacement bricks the original Imperial sizes must be precisely matched.
“Flues are lined with ‘parging’, a render mix used to prevent gases escaping through mortar joints and cracks in the structure. Parging is always somewhat roughly executed and is usually of the same mix as the brick mortar, because it is done piecemeal as the chimney stack rises. However, special mixes were also used and are found in older and larger flues. The first edition of McKay’s Building Construction in 1944, for example, recommended a mix of one part lime to three parts sand with ox hair, mixed at the rate of one pound of hair to three cubic feet of mortar. An alternative mix comprised one part lime to two parts sand and one part cow dung.”
The cast iron hob grate was the first major improvement to the 3-part stove grate. Early hob grates were used in modest homes as early as 1720.
Original hob grates were made from cast iron with hobs either side used for heating and cooking and were fitted into the chimney breast. Hob grates are often known as register grates, the difference being register grates have a register plate on the back to protect the back brickwork of the chimney, control emissions and airflow from the fire. Today “register grates” are popularly known as “hob grates” despite having the register plate on the back. The name “register grate” came because the original hob grate design with a register plate on the back was registered/ patented/ copyrighted.
Original hob grates were first used during the reigns of King George I – IV (1740-1830) and in the Regency period (1811-1820) where the Prince Regent ruled due to his father King George III’s sickness. Hob grates were popular during these periods as they were an effective way of cooking and heating at the same time. The two hobs either side of the grate allowed for plenty of room for cooking utensils and at the same time the fire would radiate heat into the room. Hob grates were used right up until the Edwardian period although the functionality of being able to cook on the hobs died out as new technologies became available. During the Edwardian period and Art Nouveau hob grates tended to have changed in style somewhat, the main difference being that they often had tiles placed in them.
The hob grates allowed for smaller coal baskets and more efficiency. The cast iron versions radiated more heat into the rooms. They came into being around 1750. The top and front were made of one single iron casting, while the remainder of the apparatus was a thin sheer iron. Being economical to produce, hob grates soon became the standard in townhouses and smaller rooms in great mansions. In poorer Georgian houses, the hob grate served as a cooking stove.
In 1796, Benjamin Thompson, Count Rumford, the polymathematical founder of the Royal Institution, wrote a pamphlet called Chimney Fireplaces. In it, Rumford described the advantages of a narrower chimney throat. Rumford applied his knowledge of heat to the improvement of fireplaces. He made them smaller and shallower with widely angled covings so they would radiate better. And he streamlined the throat, or in his words “rounded off the breast” so as to “remove those local hindrances which forcibly prevent the smoke from following its natural tendency to go up the chimney…” Rumford “put his money where his mouth was” by installing new grates in his Brompton Row, Knightsbridge, residence. “Rumford Stoves,” which brought the heat source closer to the opening and which canted the sides to increase radiation, quickly became popular among wealthy aristocrats, including the Marquis of Salisbury.
The Rumford fireplace created a sensation in London when he introduced the idea of restricting the chimney opening to increase the updraught. He and his workers changed fireplaces by inserting bricks into the hearth to make the side walls angled and added a choke to the chimney to increase the speed of air going up the flue. It effectively produced a streamlined air flow, reducing turbulence so the smoke would go up into the chimney rather than lingering and often choking the residents. Many fashionable London houses were modified to his instructions, and became smoke-free as well as more efficient. Thompson became a celebrity when news of his success became widespread. In an age when fires were the principal source of heat, this simple alteration in the design of fireplaces was copied everywhere .
Rumford fireplaces were common from 1796, when Count Rumford first wrote about them, until about 1850. Jefferson had them built at Monticello, and Thoreau listed them among the modern conveniences that everyone took for granted. There are still many original Rumford fireplaces, often buried behind newer renovations. He also invented a cast iron stove, which competed successfully with the famous Benjamin Franklin stove. Both devices gave much more control over the air flow into the fire, and were both much more efficient users of fuel. Such stoves were expensive, but saved so much fuel as to justify the cost of installation very quickly.
Further improvements were slow coming. In the 1820s and 1830s stove grates and hob grates, continued to follow the patterns of the late 1780s.