BCD 2017

116 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 1 7 and the bar is often ‘ragged’ (chiselled) or ‘upset’ (thicker at the embedded end). It may be possible to remove the ironwork with the stonework still attached, for example in the case of railing capstones. Occasionally railings are set in holes that extend all the way through the capstone, enabling the lead to be melted out from the underside. Any spalling, which can easily be caused by the heat, would be hidden within the cemented joint when the capstone is re-fixed. Where access is difficult and all other methods fail, the only option may be to cut the ironwork to allow access to drill the lead out. The ironwork would then have to be repaired. HEALTH AND SAFETY While lead has been used for centuries, today attention must be paid to the associated health and safety and environmental hazards when using this material and its compounds. The Health and Safety Executive (HSE) provides excellent advice on working with lead (see Further Information). It is highly likely that any historical paint will be lead-based and any dust will be hazardous to people in the vicinity and to the environment. Dust should be collected with a powerful vacuum cleaner that has a recommended filter system. Dust and debris should be collected in sealed containers and disposed of at an approved recycling centre. Any waste lead can be re- melted and used again. When using molten lead there are associated fire risks and care must be taken not to overheat the lead creating a lead vapour that could be inhaled. Personal hygiene is paramount and no food or drink should be consumed in the immediate area. Practitioners should use recommended personal protective equipment (PPE) including face-masks, overalls and disposable gloves. Dedicated overalls should kept for working in the designated lead working area to prevent contamination. People who regularly work in this environment should have the amount of lead in their blood monitored by having tests carried out at least every six months. This can be carried out by a GP and it is very important that the amount stays below the recommended level (see HSE and NHIG guidance in the Further Information section). REINSTATING IRONWORK When ironwork is to be fixed into new masonry, fixing holes should be made using a non-percussive system such as a diamond drill which will reduce the risk of damage from vibration. Drilled holes have smooth sides which offer little adhesion to the lead. Drilling angled holes creating a bell-shaped bottom to the hole or chiselling it square will create an effective key for the joint. All dust and debris must be removed from the hole, usually blown out with an air pump. ‘Ragging’ the iron bars can help to provide a key for the lead to fix to. It is essential that the holes are kept clean and dry. If moisture does find its way into any of the holes they can be dried out by resting a heated bar in them. Molten lead poured into a wet hole will very quickly generate steam and the pressure will spray the hot lead out. This represents a significant hazard and the wearing of full PPE including a full face mask is essential when lead pouring. Iron which is to be leaded-in should have a surface finish applied (such as lead-based or linseed oil paint) before it is placed in the socket to provide an extra level of corrosion protection. Molten lead solidifies and chills quickly so the surface finish should remain intact. Once the iron to be fixed is in position, a clay bund can be made around the bar and the area cleared ready for pouring. The lead melting area should be safely away from the work area and should be fenced off. Molten lead is poured into the hole with a small ladle. It is important to ensure that enough lead is poured in because it shrinks on cooling. Once the lead has cooled, the clay bund can be removed and any excess lead removed with a chisel. The lead can then be caulked down to form a smooth tapered surface. A piece of oak tapered to approximately 12mm square on the end grain and cut at a slight angle makes an excellent finishing tool. It is held lightly on the surface and gently hammered to produce a smooth, well-defined joint. Experience has shown that these lead fixings, if properly executed, should survive for centuries. Further Information M Boultwood and J Adkins, ‘Lead and You’, NHIG , 2013, http://nhig.org.uk/category/ articles Health and Safety Executive, ‘Working Safely with Lead’, www.hse.gov.uk/lead NHIG, Conservation Principles for Heritage Forged and Cast Ironwork , 2013, http://nhig. org.uk/standards/conservation-principles DAVID FIELD and ADRIAN LEGGE are blacksmithing tutors at the National School of Blacksmithing, Hereford & Ludlow College. The article is compiled from the combined knowledge and experience of the practitioners of the National Heritage Ironwork Group (http://nhig.org.uk) . Cracked plinth caused by corrosion and rust jacking (Photo: A Theale) Usingaclampandwedgestoliftpaling(Photo:ALegge) Cracking caused by over-caulking (Photo: A Legge) A well-defined caulked joint (Photo: P Smith)