General view of part of the molding bay showing a molder preparing a cope. The cores are seen resting on cast-iron plates attached to wheeled carriages. The drying stove can be seen in the background.
A skilled craftsman impresses the cope mold with the individual patterns which will provide the bell's inscription.
Typical clappers produced from ferritic ductile iron.
The historic buildings housing Whitechapel Bell Foundry in London.
The tuning process involves the removal of a shallow skim of metal in discrete areas from the interior of the bell.
The blacksmith's shop, one of the essential facilities in the Whitechapel foundry.
Business conditions are difficult for U.K. foundries, and closings have become fairly common, so it's difficult to grasp how one operation has been business since 1570 - 434 years. However, "bellfounders" have always stood apart from their commercial counterparts, catering as they do for a very specialized market.
Whitechapel Bell Foundry Ltd. occupies the quarter-acre site of a historic inn, known as The Artichoke on London's Whitechapel Road. Today the listed buildings with their Georgian facade house a foundry, fitting shop, and other workshops. The business has been owned by the Hughes family for exactly a century and now is managed by Alan Hughes and his wife Kethryn, the fourth generation of a bellfounding dynasty. The company is one of only two bellfoundries still trading in the U.K. Although Whitechapel's main activity is producing tower bells, they also manufacture hand bells covering a range of six and a half octaves.
Tower bells are almost entirely destined for churches. Demand varies, decade by decade: Two years ago, Whitechapel was so short of orders that it was forced to layoff some employees; Today, the company reports, business is relatively buoyant, with a six-month order book. The company employs 25 people now, of whom two work off-site in hanging the tower bells. Exports account for between one-quarter and one-third of the business.
In recent years, hand-bell ringing has become a popular pastime, and many ringers — especially in the U.K. — prefer the "tonal color" of Whitechapel bells. Catering to these customers, Whitechapel has set up a retail shop to sell and promote handbells, handchimes, hand-bell music, and a whole range of accessories and gift items.
Whitechapel's owners and workers are proud of their history, as visitors discover when they visit what amounts to a museum of bellfounding. Even the door is framed in the strickle boards the swept the core and cope for the mold for "Big Ben".
Whitechapel has produced a long line of bells, some of them household names. The foundry cast London's famous Bow Bells and those for many other churches in the city. America's Liberty Bell was cast in the foundry in 1752 followed, just over 100 years later by Big Ben for the Houses of Parliament (13.7 metric tons). Other notable bells include the Great Bell of Montreal (11.7 metric tons), the American Bicentennial Bell (5.5 metric tons) and a bell presented to Wall Street's Trinity-Church by the City of London on September 11, 2002.
Since the earliest times, bellfounders have used loam molding as the basis of their craft. The "loam" is based on a clay-rich sand containing sufficient water to give it a mud-like consistency. Traditionally, loam has also included an addition of animal hair, horse manure, and in some cases, beer. The core and the outer cope mold are swept up into shape with strickle boards, each of which are attached to rigid vertical steel rods. The technique of strickle molding, pioneered by the early bellfounders, was eventually adopted to produce cannons. Later, it became the standard method for producing steam-engine cylinders, pipe, and all manner of engineering castings using strickles or rudimentary skeleton patterns. Indeed, loam molding only disappeared with the introduction of "chemically-hardened" sands, such as those used in the CO2 process and resinbonded systems
Inherent in Whitechapel's approach to loam molding is the requirement to dry the mold and core in successive stages to remove the considerable amount of water present in the sand. This invariably results in severe crazing of the surface, a direct result of the high clay content. This is offset to some extent by the porosity imparted to the loam by the horse manure and the "reinforcement" resulting from the incorporation of animal hair. Finally, the cracks in the mold surface are filled in with a slurry based on the thicker loam.
Preparing a core for a tower bell begins with by building up an inner structure of curved red bricks, bonded together with loam, around the vertical steel spindle. The latter serves as the pivot for the strickle board, which is used to sweep up the successive layers of soft wet loam. As is normal practice in loam molding, dry cakes of loam are incorporated in the mold, stage by stage. Migration of moisture into the cakes firms up the consistency of the mass of sand and prevents slumping. The core is finally brought to shape by applying a thin coat of slurry. Then, resting on its cast-iron baseplate, the core is transferred to the stove for its final drying cycle.
The cope mold is strickled up within a perforated cast-iron flask in a similar manner. After the application of the final slurry coating, the surface is generously dusted with graphite, in preparation for imprinting the required inscriptions that invariably encircle a bell. These characters are applied by tapping the appropriate patterns into the soft sand with a light hammer.
The cope and core are baked for the last time and then united, clamped, and made ready for pouring.
Hand bells are conventionally bench molded in tight flasks, using greensand.
Traditionally, bellfounders have used coal-fired reverberatory furnaces to melt their bell-metal for larger bells. This was the case at Whitechapel until 1963, when a five-metric-ton furnace was taken out of service after 150 years. Molten metal had also been supplied by eight three-cwt coke-fired crucible furnaces.
The reverberatory furnace was replaced by a 7-metric ton, oil-fired rotary furnace. The unit was built inhouse, with input from the Eyre Smelting Co. and the British Non-Ferrous Metals Research Association. Today, this furnace is only used when the foundry is called upon to cast a very large bell. Normally, sufficient metal can be obtained from an oil-fired 1.25-metric ton Morgan tilting crucible furnace and/or a Morgan 60-lb lift-out crucible furnace. This latter unit can actually melt 100 lb with an appropriate crucible.
Normally, molds are prepared on a three-week cycle, culminating with their pouring on a Friday, allowing them to be knocked out on the following Monday. The necessary metal would be provided by the 1.25-metric-ton crucible furnace that would normally be used for two (or, or rare occasions, three) successive heats. Molds for hand-bells are cast, when ready, from metal from the 60 lb crucible furnace.
A normal charge will incorporate 80 Cu/20 Sn ingot borings and broken bell metal — unless bells are being recast, in which case most of the charge will originate from the original bells. Whitechapel buys 20%-tin bell-metal ingot from Brookside Metals, as this is the lowest tin content that the foundry would employ in any conceivable circumstance. Then, they add more electrolytic tin to the melt to bring the metal up to the required composition for any specific bell. Normally, the tin content of a tower bell is 21.5% to 24%, depending on the bell's size. The larger the bell, the lower the proportion of tin. The bell-metal purchased from Brookside Metals is guaranteed to have a total impurity level of not more than 1% for the casting of tower bells, and 0.1% for the casting of musical handbells.
Having retrieved the tower bell from the mold, the next stage in production is tuning, the peak of the bellfounder's specialized skills. Whereas there are several basic factors contributing to how a bell will finally sound - namely, shape, the thickness at any given point related to the diameter, and the composition of the bell metal — tuning is the ultimate step. It is achieved by judicious removal of metal from the inside of the bell using a vertical lathe. The tone of a bell has been largely predetermined by the above factors. However, equally important is pitch. There are some 40 discernible harmonic tones or notes present in a bell. Of these, the bellfounder attempts to tune the five most powerful notes: the strike note, which sounds on the impact of the clapper; the hum note, which swells up immediately afterwards, and which is tuned to one octave below the strike note; the nominal, one octave above the strike note; the minor third; and the fifth above the strike note.
The tuner's skill is to remove bands of metal within the bell that will bring the harmonic tones into relationship with one another and flatten each in turn to achieve the final pitch. In the past, the tuner employed tuning forks to guide him in his task. Today, the bellfounder uses an electronic instrument to determine the value of the notes and their sharpness on the harmonic scale.
Whitechapel Bell Foundry has two vertical lathes employed in tuning.
Tower fitting and assembly
Within the Whitechapel site, a spacious shop is used to construct bell frames and other parts to be incorporated in the bell towers. This provides facilities for fabrication, general machining, and blacksmithing. Traditionally, bell clappers were forged from wrought iron. However, for the last several decades, these components have been cast in ferritic ductile iron.
Elsewhere, on an upper floor, space is set aside for building the wheels that have an essential role in swinging the bells, and a workshop for the tuning, polishing, and fitting out of handbells.
Not surprisingly, Whitechapel Bell Foundry's place in the history of London is widely recognised. Although the foundry cannot be accessed during working hours, tours of the premises are offered on Saturdays by appointment, and the retail shop and handbell music room are open to visitors Monday through Friday, during business hours.