We were recently invited to Marlborough college to inspect bronze staining on the Portland Stone structure of the Richard Corfield Memorial.
On the south side of the memorial, staining has taken place all the way down to the plinth while on the north side, the plaque is set back into the stone with evidence of strong staining beneath.
A bronze specialist is being appointed to undertake cleaning and re-patination of both the bronze bust and plaque in situ. But there is a concern that if only the exposed surface of the bronze work is to be cleaned and re-patinated in situ then the staining is almost guaranteed to quickly reappear.
The staining on the north side below the plaque could also be coming from the reverse of the plaque.
It is recommended that the plaque should be removed so it can be treated and sealed on the reverse side, even if the bust isn’t removed at this time.
If the bronze items are removed, then a more thorough and reliable poulticing action can be carried out to remove the verdigris using a poultice or Stonehealth’s Calcimex.
A number of applications may be required to remove the staining which would have been drawn in well below the surface. Frequently the first poultice may look as if it is making matters worse as it is drawing the staining to the surface and subsequent applications should gradually remove the verdigris.