Through the glass decoratively

Polly Gibson looks into the types of glass used to enliven London’s front doors.

You learn something new everyday; well I do at any rate. Today I’ve learned that glass is neither a ‘solid’ nor a ‘liquid’ – technically it’s apparently somewhere between the two and is classed as an ‘amorphous solid’. And it seems that the famous old urban myth about very old pieces of glass gradually becoming thicker at the bottom over the years is completely wrong! Window glass doesn’t flow downwards due to gravity. Differences in thicknesses in old panes of glass are due to the way they were made, not to the passage of time.

Front doors, and the fanlights above them, have long been used to admit light into what would otherwise be quite dark entrance hallways. Georgian, Victorian and Edwardian front doors between them show all manner of variations in the use of decorative glass panels. Leaded lights and stained glass were discussed in an earlier Bespoke Front Door blog – ‘Pieces of Light’ – so today I will concentrate on etched glass and cut glass. Grinding, cutting and polishing are about the oldest techniques used to decorate glass. It was to these our ancestors turned in preference to using large areas of plain obscured glass, a look which has more appeal to 21st century eyes.

A four panel Victorian front door with sandblasted glass
A four panel Victorian front door with sandblasted glass

Patterns were applied to initially clear glass by using either acidic or abrasive processes. Sand-blasting creates a frosted look by making tiny scratches in the surface of the glass. If part of the surface is protected by a vinyl stencil or by inking-on a design before the sand (or acid) arrives then, when the ink is wiped away or the vinyl peeled back, a permanent pattern remains, formed from alternating clear and etched areas. For a fully obscured panel it is necessary to first sand-blast the entire background and then to etch a decorative patterns onto this using acid.

A floral design which has been brilliant cut into sandblasted glass
A floral design which has been brilliant cut into sandblasted glass

Brilliant cutting of glass is a specialised and highly skilled craft. A design is drawn onto the surface and the pane is then maneuvered by hand against a profiled cutting wheel so that grooves are cut into its surface, carefully following the lines of the pattern. Traditionally, the glass was then obscured by hand, using a fine grinding paste. The brilliant cuts, being safely below the flat surface, remained beautifully bright and polished. Great examples of this craft still survive in period front doors across many parts of London.

The heat is on

You may treasure your bespoke front door or your lovingly restored original. Sadly, few others will treat it as gently as you do. London’s front doors have a hard life. They are likely to get pushed open and slammed shut by visitors using their toe-caps, heels, buggy-wheels, bicycles, skate-boards or the sharp corners of boxes and suit-cases. The resulting chips and scratches to the paint-finish are not just unsightly; they can expose the timber to moisture penetration. Moreover, to the familiar natural hazards presented by wind and rain, this summer we now have to add the harmful effect of prolonged exposure to strong sunlight. Your front door needs all the help it can get and paint is its first line of defence.

Black four panel front door in Chelsea
Black four panel front door in Chelsea

Wood does not benefit from frequent changes in temperature and humidity. Like most materials it expands when heated and contracts on cooling. Grain direction is important; lengthwise, timbers expand far less than steel when heated but across the grain movement due to temperature changes can be up to ten times greater than the linear movement. The most significant movements in timber result from changes in moisture content but these changes are frequently temperature-related. Warmer air increases the rate of exchange of moisture within the timber. Cells at the surface of a piece of wood will exchange moisture with the air very quickly but core cells will lag significantly – setting up stresses. Absorbing air-borne moisture causes timber to swell and ultimately to split along the grain or to warp.

The paint applied to London’s front doors is therefore not purely decorative; it serves to protect the timber from moisture penetration. The colour pigments in your chosen paint either absorb or reflect the light falling on the door’s surface. A white-painted door reflects most of the light falling on it. A red door absorbs every colour except red – which is then reflected back into your eyes. A black door absorbs all of the light and, since light is energy, that energy is converted into heat and emitted by the door at the infrared level of the spectrum. In simple terms, the surface of a black door exposed to sunlight becomes hotter to the touch than the surface of a white-painted door and as a result is more prone to expansion. If this movement exceeds the elasticity of the paint, cracks will develop and, consequently, movement due to moisture exchanges will accelerate.

If you simply have to have a dark colour then Accoya timber is essential, hardwood simply won’t cut the mustard. Accoya is the most stable timber that we know of and will help keep thermal expansion to a minimum but do bear in mind that with dark colours, you are pushing your door to its limits.

Paint it black, Mick? I don’t think so!

Making an entrance: Part 2

London is not one of Europe’s great ‘planned’ cities. It feels more like a collection of distinct localities – one might even say ‘villages’ – than a coherent, homogenous, whole. The City itself has been continuously inhabited and built-over since Roman times but the outer areas, to the north, south, east and west of the original ‘square mile’, developed at different times and with different characteristics as ‘Greater London’ came into being. New districts were added in successive centuries, with suburbs developing very rapidly during the Victorian and Edwardian eras. The 1890s saw the beginnings of an electrified underground railway which greatly accelerated London’s urban sprawl. In the twentieth century, as expansion continued, some of the Victorian suburbs became the less desirable ‘inner’ suburbs and by the mid-century were suffering an interval of decay and neglect. During the 1920s and 1930s, London’s outward suburban expansion continued to such an extent that it had to be forcibly halted by the imposition of a ‘Green Belt’ at the end of the 1940s.

More than in any other European capital city, well-to-do Londoners have traditionally aspired to live in individual houses rather than in tenement blocks. The Victorians could seldom resist the temptation to call even small terraced dwellings “villas” although the word properly applies to substantial houses in the countryside. Grand architectural schemes are rare in London’s history and where they do occur, as in John Nash’s Park Crescent, the overall design necessarily takes precedence over identification of the entrances to separate dwellings. In the photograph below, paired ionic columns suggest a colonnade at street-level which unifies and dominates the two quadrant arms. Nash’s colonnade was illusory; railings, steps and light-wells prevent its use as an actual place to promenade. The various shared entrances are almost hidden from view until you draw level with them.

Georgian front doors
Park Crescent 1812: only two quadrants were actually built of the huge circus Nash planned at the southern end of Regent’s Park.

With urban space always in short supply, city buildings are necessarily crammed together and entrances can offer one of the few opportunities to distinguish the dwellings, one from another. By contrast with Park Crescent, in the photograph below, the building is still conceived as a unitary design but the projecting porches with their neo-classical detailing set up a rhythm which confirms the existence of separate households.

Victorian front doors
Notting Hill: A grand 1840s terrace with a clearly expressed piano nobile above the individual projecting porches.

Building houses in squares around a central garden was a design solution successfully used in the Georgian and early Victorian periods. The monolithic character of the buildings along each side of the square is relieved by setting forward the houses at the ends or in the centre of terraces and by careful variations in the detailing and spacing of windows. Again, the attention given to the entrances establishes individual identity within the greater composition.

Georgian front doors
Mid 19th century terraced housing in Highbury, north London.

Please click here for Making an Entrance: part 1

Falling apart at the seams

Why do old doors fail?

It’s some test, the ‘Test of Time’ and doors are no exception. Wooden front doors have been around as long as we’ve lived in buildings. In the right conditions, wood is a very durable material, lasting hundreds of years. It is resistant to heat, frost, corrosion and pollution. What wood doesn’t like is movement caused by frequent changes in temperature and humidity; otherwise known as ‘sunlight’ and ‘driving rain’.

Period front doors have been constructed in a similar way for around two thousand years. Separate pieces of dried timber are joined together using mortise and tenon joints assisted by glue and wedges. The glue bonds the surfaces and wedges are driven-in to provide frictional resistance to movement. Unsealed timber will always gain or lose moisture until it is in equilibrium with its surroundings. Changes in temperature and humidity cause volume changes which are not equal in all directions. They set up stresses which can only be relieved by movement: either the timber splits along the lines of its grain or cracks develop at the joints as the pieces separate. Once a crack opens, moisture can penetrate deeper and further, harmful, movement is inevitable.

Georgian front door in south London
This lovely, Georgian front door in south east London is over 150 years old

We ask a lot of our doors, especially the external ones. They experience all the vagaries of our climate on one side and the warmth and relative dryness of a centrally-heated home on the other. Not that life is necessarily very much easier for some internal doors. Kitchen doors and bathroom doors are especially vulnerable to the consequences of having a warm and steamy environment on one side and drier, cooler, air on the other. In other rooms, we leave doors open for long periods with a radiator close by, pumping its heat into only one side of the timber.

Victorian front door
Nothing lasts forever! A Victorian front door in St. Leonards- on- Sea

Noel smiled when he looked at the 100 year old Victorian front door on my house. All this winter I’ve been pushing draught-excluders into the gaps around it – largely to no avail – and then on damp days it fits so snugly into its frame that I can hardly get it open. Which is why I had called him round.
“This door needs planing to stop it sticking,” I told him.
“Look at the top rail,” he replied. “Can you see how there’s a wedge-shaped gap between the top of the door and the frame; it’s very small at the hinge side, and very wide above the locks?”
Next he pointed to where the door was binding on the step, at the bottom corner, furthest from the hinges.
“These two old hinges can no longer carry the weight,” said Noel. “Over the years, the loops around the central pins have worn away until now they’re more like spirals. That’s why your door sticks and, from now on, this one always will. You need new hinges as well as a new door. Let’s face it, after a century of use they’ve earned their keep many times over.”
“But if I get a nice new door, won’t the same thing happen again?”
“Eventually,” he said, “Yes, it probably will. But if it starts to stick in the winter of 2113, don’t hesitate to call me back.”