Agriculture Reference
In-Depth Information
last rubbers produced from Thomas Lawrence works these were traditionally cut
using the bow saw and various profiled cutting boxes made to templets obtained
from the original niche bricks. The work was quite rightly recognised by the
BDA with an award for the excellence of craftsmanship in 1981. This, however,
was quite a rare example of gauged work being employed and this situation
remained true throughout the 1990s and to a large degree remains so today (in
2007). Much has been done by the author to revive the knowledge and skills of
gauged work through his work with apprentices at Bedford College from 1987 to
1992, his publication on the subject (Lynch, 1990, revised 2006) and numerous
other works since then which are of record.
The Lime Revival and its Use for Gauged Work
From the late 1970s a revival in the knowledge and use of lime-based mortars
began, though not within the modern construction industry, being almost
exclusively linked to building conservation work; though this is slowly being
addressed, with positive input among various bodies; including the Building
Limes Forum (BLF). The lack of education in traditional materials within craft
apprenticeships and training programmes meant simple terms like hydrated
and hydraulic were, and still are, confused by a great many. It was not uncom-
mon to find bricklayers trying to make a lime putty for gauged work using
bagged hydrated 'High-Calcium' lime from a Builders Merchants, a product
solely intended for use as a plasticiser in cement: sand mortars, instead of
properly slaked lime putty made from quicklime. In the early years of the 'lime
revival' emphasis tended to centre on the benefits of use of pure non-hydrau-
lic lime putty, due to its sacrificial nature on certain remedial works. This, how-
ever, was at the expense of a wider knowledge and pragmatic understanding
of types of greystone or hydraulic limes and alternative slaking techniques and
mortar preparation, which historically were preferred by masons and bricklay-
ers (Lynch, 1998).
The specialist skills of conservators working on historic buildings during the
lime revival included research into traditional materials and the ways that these
could be matched for sympathetic repairs. The addition of pozzolans to pure
non-hydraulic lime has a long history, particularly where hydraulic limes are
not available. It is possible to produce the equivalent of a feebly hydraulic or
grey chalk lime in this way but this does require considerable experience and
testing to ensure the matching mix is of the correct composition to achieve the
set and weathering qualities required. The range of pozzolans available is wide
and the history of their application varied. A list of pozzolans, their source and
the way they were used historically is set out in Building With Lime (Holmes and
Wingate, 2002; Appendix 2 on pages 282 to 284).
 
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