Pulhamite  is a great Victorian invention! ( or two actually … read on! ) James and Obadiah Pulham in the 1840s pioneered the creation of landscape features using “… stone-modelling skills to form artificial rocks from heaps of old bricks and rubble covered in cement, and ‘sculpted’ the surfaces to simulate the colour and texture of natural stone.”  and making a type of terracotta, baked clay.
The Pulham’s business was successful for roughly 100 years, only disappearing after WW2, and their work graced many a city park and rural and urban mansion gardens. 
Pulhamite is not a strictly building material, as in a structural material used for buildings as the Building London blog focuses on, being mainly ornamental, but Pulhamite was used for some massive features in Ramsgate and Folkestone, a ‘castle’ folly in Hertfordshire at Bennington and a bridge in Buckingham Palace gardens!
Anyway many materials this blog will cover which appear to be structural actually were just facings, covering brick or concrete structures and not structural. Granite was used to face concrete on 19thC Thames embankments and even The Elizabeth Tower aka Big Ben Tower is, somewhat surprisingly, a brick structure, with a stone facing!
Pulhamite however was also the name the Pulhams used for a stone coloured Terracotta which was used to make artificial stone ornaments, statues, giant vases, balustrades and fountains. 
The London Gardens Trust states, of gardens, “Building rockwork … was expensive, particularly when the rock had to be imported from elsewhere in the UK or even from abroad. So enterprising builders and landscape architects came up with a range of ingenious alternatives in the form of artificial rockwork.
One of the most successful creators and suppliers of artificial rockwork and features was the firm of James Pulham who, for over a century from the 1830s to the 1940s, designed and built rockeries, rock gardens and grottoes in parks and gardens all around the UK, using their proprietary artificial cement render, called Pulhamite.
Pulhamite took several forms but is most recognisable as a distinctive pinkish, lime-based cement. This was used by the firm from the 1830s to the 1870s to cover brick-built foundations and was worked to simulate real rocks. Great care was taken to make the rockwork realistic, even copying the local geology and including local rocks in the finished product. Pulhamite was in great demand during this period, with over 170 major projects constructed around the UK.
Pulham prided themselves on the quality of their product and ‘Durability guaranteed’ was their company slogan. This durability was to be tested to its limit in public parks during the twentieth century, when lack of maintenance allowed weeds and scrub trees to encroach on many of the features and the water was turned off on the waterfalls.” 
The incentives for Pulhamite included cost, it being significantly cheaper than real stone, but also after the disaster of the stone at the House of Parliament, durability was a key issue for many builders/landscapers – “The mid C19th was an innovative time for the development of artificial stones, the hope being that each would be less susceptible to weathering decay than natural stone – and cheaper too. The topic was kept in the public eye by the rapid decay in London’s sulphurous atmosphere of the Magnesian Limestones that had been used only a decade or so earlier for the building of the new Houses of Parliament” 
The workers were called ‘rock workers’ … “[Pulhamite] … is a miraculous Victorian invention of hefty stones … made using a mixture of rubble and cement, cunningly modelled to simulate the texture and colour of natural stone. The skilled craftsmen who made them were known as ‘rock workers’.” 
BuildingConservation.com, which plays a key role in the movement and practice of conserving historic buildings in the UK, states of Pulhamite, and it’s worth quoting in full, “The Pulhamite Rock-Work system was described by Pulham … as: ‘the building up of natural stone in complete imitation of a portion of rocky cliff with stratified or unstratified stone or rock, and joined, where necessary, with Pulham’s cement, made of the same colour and texture, as lime or sandstone, and tufa. Where no real stone or rock exists, at or near, and too expensive to get then the Pulhamite formation is adopted. The core is formed by building up burrs, rough bricks, rubble etc, to the rude rocky shapes; then covered with cements of the colour, form and texture of the rock, which may be considered to be the most natural or nearest to the locality. Sometimes real rock or stone is used with artificial, for economy and effect; in thin strata, where large blocks of real stone are too expensive, this adds to the naturalness of the appearance, and not too much cost’.
Frequently hydraulic lime was used as the masonry construction mortar, and a series of large cantilever stone slabs, often entirely covered with the Pulham cement mortar, was used to provide projecting plant pockets and strata. Rock embankments and walling could include small sandstone lintels buried below the surface, off which further masonry walling was constructed. In grottoes, the use of natural limestone such as tufa was common, bonded to the walls with Roman cement and the areas between were made up with colour-matched mortar (often hydraulic lime based), thrown on to give a suitable rough texture.
..the Pulhamite Artificial Rockwork and later 19th-century artificial stone often used pigments to colour the pale cement binders to provide the necessary imitation. In Pulhamite rockwork, mortars of different pigmented colour were carefully manipulated and applied by hand to imitate the variations of colour found within the rock face and strata. This is not always immediately obvious because the rockwork is often now covered in algae, moss, or other deposits. As well as pigments, the Pulhams also used mortar inclusions such as shells, or impressed designs which imitated fossil bands for example. The later 19th-century artificial stones tended to be more frequently pigmented with reds and browns, no doubt in imitation of red sandstone or even terracotta.
There is no evidence that Pulhamite artificial rockworks were ever pre-cast and placed, all examples seen by the author have been built in situ.” 
For more in depth reading on Pulhamite, the English Heritage document ‘Durability guaranteed: Pulhamite rockwork, It’s conservation and Repair’ is excellent,  though the brilliant website  and associated book ‘Rock Landscapes: The Pulham Legacy: Rock Gardens, Grottoes, Ferneries, Follies, Fountains and Garden Ornaments’ both by Claude Hitchings is the absolute bible, including listing all the sites ever linked with Pulhamite either in manufacture or structures built. 
The London Connection – Manufacture
The London connection to Pulhamite is significant. Not only was the Pulham’s base in initially London and then just outside, many of the projects were in London at least initially.
The business was first established in Tottenham, though Building London has not yet been able to identify where precisely, yet, in 1834. In 1838 the Pulhams moved to Hoddesdon and then in 1845 or 1848 to nearby Broxbourne where they built 6 kilns to manufacture the terracotta Pulhamite, and where they manufactured their special cement, which was distributed via depots in Tottenham ( maybe their old base? ) and Brixton. I am guessing they used the Lea Navigation and railway for transport. 
Pulham.org states : “James 2 set up a manufactory in Broxbourne, Hertfordshire, in 1845, in which to manufacture a wide range of extremely high-quality terracotta garden ornaments, such as vases, urns, sundials, terminals, seats, figures, fountains and balustrading etc, most of which were designed either by James 2 himself, or his younger brother, Michael Angelo Pulham.” 
Building London visited the remains of the Broxbourne works in 2021, following on the footsteps of The Art Journal in 1859! This area, with the church, New River, Old Mills and millstreams going down to the River Lea remains very pretty and pleasant even if the wider area has had some major development…
“ In the pretty and pleasant village of Broxbourne, reached by the Eastern Counties Railway, and distant nineteen miles from the Metropolis, there is a small, but very interesting, manufactory of works in terra-cotta, to which we desire to conduct our readers. It is situated on the Lea, where its current runs side by side with “the New River.” The site is historic; it is close by the famous Rye House, and contains the quiet and unobtrusive hostelry, existing to-day as it did two centuries ago, where honest Izaak Walton met and chatted with his friends when they used to go “a fishing” on the banks of the fertile stream, when the wind was south, and the trees were putting on their robes of green. We note these facts as additional inducements to attract visitors to this Manufactory, located, as it is, in a neighbourhood full of interest and rich in the picturesque….In the terra-cotta works of Mr. James Pulham, at Broxbourne, there is very gratifying evidence that the science of his manufacture has received due attention. Hence he has been enabled to produce his “granulated stone-like terra-cotta,” and his “ natural stone-colour cement.” Both are materials of great value and importance—both have already proved their practical capabilities, and, without doubt, when they become better known, both will be brought into widely extended use.” 
Today the bottlekiln can be found by taking a small footpath off Station Road, very close to Broxbourne station, with Kingfisher Close on your right and Beech House on the left. Walk down 30 yards and you will be at the kiln.
The kiln is Grade 11 listed,  was restored in 1985 and again in 2016/2017 and is open to the public.  Surprisingly the factory buildings from the 19thC seem to have survived till 1966! “The manufactory site was left to fall into disrepair and was demolished in 1966 to make way for new housing and a larger car park for Broxbourne railway station. Today, all that remains of the factory is one of six original brick kilns and a horse-drawn ‘puddling’ wheel that was used for mixing terracotta. Both structures are Grade II listed.” 
This was the Part 1 and there will be some site specific posts of Pulhamite features in London.
This is a great site to visit as it’s not only dead easy to get too from London, but it’s a lovely area with the crystal clear New River, the ancient St Augustine’s Church,  the Old Mill streams AND the River Lea, with boat hire available  and 100s of acres of the Lea Valley Park to walk and cycle in! So a great day out from London AND if you do cycle there you go through Waltham Abbey with it’s amazing old Abbey walls and London Bridge connections (see previous BL posts) 
Broxbourne is about 30 minutes from London out of Liverpool Street or 40 minutes from Oxford Circus changing at Seven Sisters.
You can easily walk or cycle, straight up the Lea Valley – Google says it would take an hour and a half to cycle the 17 miles from Liverpool Street. And once down by the Lea it is off-road on the canal path all the way, though that can be quite rough cycling at times.
 ‘A visit to the Terracotta works of James Pulham, Broxbourne’ – The Art Journal 1859 https://archive.org/stream/artjournal1859lond/artjournal1859lond_djvu.txt