SMOKE AND STONES

Evening Post, Volume CXVI, Issue 49, 26 August 1933, Page 14

SMOKE AND STONES

BUILDINGS DECAY

EFFECTS IN WELLINGTON

POLLUTED ATMOSPHERE

Lamentations were heard at the summer meeting in London of the National Smoke Abatement Society about the damage caused to buildings and monuments by atmospheric pollution. Sir Frank Baincs described atmospheric pollution as the destructive canker of the age and one which will finally render unintelligible the readings of history in all national monuments. He estimated the cost of making good the results of atmospheric impurities to buildings throughout the country to be £55,000,000 at a minimum. The actual damage, he was convinced, if carefully calculated from all sources, would probably be found to be far in excess of that figure. Was it not amazing, therefore, he asked, that methods of prevention were attacked on the score of the cost of their institution? After speaking of his won: in connection with the stonework of the House of Parliament, he said that the regulation cleaning of the Nurse Cavell Memorial four times a year had been increased to six, but ho had eomo to the conclusion that the dingy yellow discoloration would spread slowly over the whole of the marble work ; and that it was due to atmospheric impurity. At Sandon, five miles from Stafford, the stone of the War Memorial was blistered, with definite eruptions and burst surfaces which left irregular shaped holes. Sir Frank Baid that while legislation was tentatively reaching out in an endeavour to deal with what were felt to be the controllable factors of smoke emission—factories, power stations, and large industrial units —Parliament was not prepared to ' deal with the critical problem of the domestic fire or the very destructive sulphur gases. Local and unicipal bodies wore taking an increased interest in planning restrictions to eliminate some part of the nuisance. He paid tribute to the work of the National Smoke Abatement Society in calling conferences of local authorities to arrange for' formation of area committees. Wellington has no National Smoke 'Abatement Society to express concern at the destruction being slowly wrought to the various buildings and monuments in New Zealand's capital city, and naturally things are not quite as bad in Wellington as they are in London, for Wellington is a trifle younger than London, and Wellington's output into the atmosphere of smoke and other impurities is not on the same grand scale as London's. Nevertheless, that destruction is going on in Wellington is plainly visible to these who know where to look for evidence and to those who can recognise the symptoms when they see them. Wellington's atmosphere is by no means pure in spite of the gentle draughts periodically supplied' by Nature. Much coal, both in factory and home, is burnt in Wellington, and since New Zealand coals contain much sulphur, the air is polluted with sulphuric acid and other chemical compounds which slowly but inevitably destroy stone which has been used for building purposes. VARIETY IN BUILDING STONES. Several kinds of building stones have been used in the construction of Wellington's buildings since the time it grew out of the stage of being a mere collection of wooden huts. All these stones show signs of weathering, some to an alarming extent and others not so markedly. Modern concrete construction methods have to a large extent done away with the use of building stone, but architects still prefer to ■use stone for facings, and they are confronted by the knotty problem as to which kind or kinds of stone stand up best to the prevailing atmospheric conditions. Once upon a time Oamaru stone was largely favoured, and this, in the country and away from a polluted atmosphere, is undoubtedly one of the best of the native building stones. But in a city like Wellington it scales badly owing to the sulphuric acid in the atmosphere. This impurity is a product from the burning of the sulphurous coals; the acid sets up a chemical reaction on the surface of the stone and allows Tain to penetrate its pores. When it dries, crystallisation sets in on the skin and the stone blisters. The Customhouse building provides a visual demonstration of this process. The sulphur in New Zealand coals also badly affects Portland stone, the figures outside the G.P.O. Building ■being in a decidedly sorry state from this cause. The main portion of the G.P.O. is built of granite from Nelson. This is a coarse-grained, very incoherent stone, which crumbles under the effect of weather. It has, however, been treated with preservative and thereby had its appearance bettered. The Public Trust Building is also built of granite, but the stone for this building came from a different quarry which produced stone of a better quality than that used for the G.P.0., hence signs of weathering are not so obvious. Coromandel granite, which can be seen on the steps and approaches of the Bowen Street War Memorial, is a very permanent building stone. It contains, however, a little sulphide of iron, and where rain accumulates on it •a rusty effect is produced. Polished granite is largely, used for shop fronts and suchlike purposes. It is permanent and keeps its polish, not dissolving like marble. DISAPPOINTING MAKBLES. Polished slabs of marble, from Taka]ca or elsewhere, arc disappointing when exposed to weathering conditions. Their tints disappear after a time, and they become white owing to atmospheric action. The New Zealaud marble, which can be seen in the Parliament Buildings, the State Fire Office, and elsewhere, has a nasty habit of turn-' ing black. This is due to the- action of rain and to the presence of sulphato of lime on the surface. This allows particles of soot to become embedded on the surface, there being a cure, however, in spraying or washing. Whangnrei marble is used for inside work. No polished marble will withstand weather influences. The carbonic acid in the air dissolves the particles on the surface of the stone; the polish disappears, mid colour turns to whiteness. Carrara marble suffers from the effects of the atmosphere much like New Zealand's own marbles. Parts of the Balla'nco statue in the Parliamentary grounds show the effect of weathering on this marble very clearly. Over the stains on tho War Memorial^ whether they bo green or brown, intentional or otherwise, it may be kinder to draw a veil. Sydney sandstone has been used for several of Wellington's buildings, ono example being the A.M.P. Building. This stone has a creamy colour at first, but the oxygen of the air combines with an iron salt in it and tho stone gradually assumes a rusty tint. Although it is inclined to scale a little, it makes a gond and lasting building stone. New Zealand sandstone, to be seen at the base of the G.P.0., decays in patches, and is not strong enough to be c really good building stone. For heavy work, a Melbourne basalt has bee.n used in several of Wellington's

of tho Town Hall. This is a dark coloured stone, not particularly hand- j some, but is pretty permanent and is useful as it can be quarried in big pieces. Volcanic breccia from Port Chalmers has also been used in big pieces for heavy work, notably in the basement of the Custom House buildings. This is a fine-grained material of a greenish tint, which weathers irregularly. Trachyte, used in the T. and G. Building, is another good building stone. THE BEST STONE OF ALL. The best building stone of all, however, is ono which has only lately received the recognition due to it. This is the vitric tuff from Putaruru, near Arapuni, and it is largely due to Dr. P. Marshall that its merits have lately come to bo appreciated. Buildings erected of it fifty years ago showu no sign of weathering even today, and it has stood every test to which a building stone can be subjected. It is to be found in enormous quantities— enough to rebuild Wellington many times over —and stone of every grade and texture can be quarried. As a locally-produced building stone it has no equal, and it can more than hold its own against all imported stones. Wellington's Carillon tower is built of it, and it is the stone which has been chosen for the new museum and art gallery building. An enlightened society of a hundred years hence may see to it that Wellington's atmosphere is not polluted by smoke and other noxious effluvia as it is at present. But in the meantime all our stone buildings will go on deteriorating to a greater or lesser extent and signs of weathering will progressively increase. The time to found a smoke abatement society would be before irreparable damage is done.