The famous west front of Wells Cathedral has undergone restoration on a number of occasions, but now, for the first time, the stone is also being cleaned. At the present time the north-west, or Bubwith, tower has been cleaned and restored and can be compared with the central portion which has not yet been tackled. The south-west, or Harewell, tower, is currently scaffolded and under treatment.

The west front is built of Doulting Stone, a bioclastic limestone consisting largely of crinoid ossicles. It is a local variant of the Upper Inferior Oolite. Apart from the commercially valuable outcrop at Doulting, east of Shepton Mallet, the beds in slightly altered form (as ‘Doulting Stone equivalent’) were traced along the outcrop to the Bath area by L Richardson in his researches of half a century ago. The ground between Doulting and the hamlet of Chelynch, to the north, is covered with extensive old quarries, now largely wooded. One or two quarry faces are still worked in the south part of this area, and supply the stone for the cathedral restoration.

Doulting Stone, on weathered surfaces, such as may be seen on the lowest part of the west front, shows a distinctive coarsely granular texture. On close inspection some of the granules can usually be recognised as crinoid stem ossicles, the position of the canal which pierced each ossicle being visible as a tiny dot. Having learnt to recognise the stone on the cathedral, look for it on other buildings in Wells! (A number of other building stones are also in common use).

Although some of the Doulting on the west front has failed, the buttress to the right of the northern doorway carries a well-preserved inscription which is dated to about 1350. It is a witness to the lasting qualities of the stone at its best.

Conspicuous on the cleaned part of the front are pale grey shafts which stand clear of the rest of the masonry. The longest, at the angles of the buttresses, are 23 feet long and only about five inches in diameter. They look structurally improbable; they are, in fact, made in a number of sections and are tied to the masonry behind at intervals by bronze rods. The rock used is an Irish Carboniferous Limestone called ‘Kilkenny Marble’ after its source. It is not an original part of the building, but was put in about 1870 to replace decayed Blue Lias limestone.

Blue Lias occurs close to Wells, for example in the now overgrown section at the New Cut, Milton (the 8-figure grid reference is ST 5490 4723 in case you want to look for it).

But these beds are coarser-grained than the material in the cathedral, which probably came from a little away, around Glastonbury and Street. A little of the original Blue Lias remains: both it and the Kilkenny Marble can shafts flanking the central west door - see if you can distinguish them. The central pillar here is a replacement made of Purbeck Marble.

The Blue Lias occurs in thin beds (mostly less than a foot thick) and long shafts naturally have to be cut parallel to the bedding. This, together with the fact that the limestones are impure (up to 20% clay) has caused most of the Lias on the outside of the cathedral to decay, and much of it had fallen out by 1870. Well preserved Blue Lias may be seen inside the west front, and in the Chapter House.

A fourth type of stone occurs on the west front: a soft, creamy-white limestone used for small heads flanking the north and south doors, and for foliage and figures inserted between the mouldings of the arch over the centre door. All these occurrences are probably insertions made some time after the front was completed. This stone has been referred to as White Lias, but is probably not. It has not yet been identified with certainty.

The famous thirteenth-century statues, originally over 300 in number, are mostly carved out of Doulting Stone. The stone used is of very variable quality, some of it being of very shelly varieties which are not used for the structural masonry. Possibly the quality was not felt to matter, since all the figures were originally painted and gilded. If this was the case it was unfortunate, as some of the figures have weathered very badly. In some cases stone has flaked away along the bedding, which is usually parallel to the fronts of the figures. In others a harder skin has formed which precariously preserves some of the original surface, while material has been washed out behind it leaving large cavities.

The front is being cleaned by washing with fine sprays of water. Defective masonry is replaced with new work carved on the spot, about a dozen masons being currently employed. The figures are being treated with lime water and discreetly repaired, but missing parts are not being replaced. A proprietary silicone treatment, intended to resist the penetration of damp, was tried on three figures, but was felt to produce a dull appearance and was discontinued. The figures in question may be seen on the east face of the north-west tower.

The front at present is an instructive sight for a geologist. If more ‘real’ geology is required, a visit could be combined with a search for outcrops of the stones used.