5th Update: 10th August 2015
From the outset work has proceeded from the west to the east side of the greenhouse. The west side was in better repair and so restoration techniques could be tested there more easily, particularly in determining how much glass would need to be removed and how much would be lost in the process. Metal restoration has now been completed on about 70% of the building, though the remainder is going to be the most challenging.
The glazers have now arrived on site. Starting at the west side they are now replacing the fish scale glass on the curved part of the roof. Where it still exists the same pane of glass is replaced in the exact position whence it was removed. This is not mere conservation pedantry but has a practical reason. Contrary to appearance, the gaps between the glazing bars, thanks to warping and structural movement, are not the same. Panes often only fit in the slot from which they came. Where panes were missing, the glaziers cut new ones using reeded glass taken from the casement frames and elevations. To give a consistent frontage, the curved part of the roof will only have in it narrow reeded glass.
The time consuming part of this is the puttying. Where glass is being put back, a thin layer of putty is put on the flange on the glazing bar. The pane is stuck to that and then a thicker putty fillet put on the outer side. This has to be shaped and smoothed around each pane. Puttying, rather like pointing, has a major impact on the final look of the surface; we have to strike a balance between a sufficient quantity of putty to hold the glass but not so much as to coarsen the delicate lines of the glazing bars. The putty must look consistent and smooth. It will take some weeks to dry thoroughly, at which time it will be painted.
Within the greenhouse a number of small enhancements have been made. The roof has now been firmly attached to the internal supporting beam, as opposed to merely resting on it, by means of small hooks. The main vine wires have been straightened and though we do not intend to reinstate the cross wiring between the main stays, the small catches which would permit this have been restored.