Ferramenta
Wrought iron ferramenta bars can be of great concern in respect to the damage caused to the stonework of a window.
The damage is caused where the ferramenta enters the stone, the metalwork corrodes causing the base metal to laminate. Lamination is where the wrought iron through corrosion splits into layers more corrosion occurs and the metal expands... This expansion in conjunction with the weakening caused by the chemical reaction between the corrosion and the stone causes damage to the mullions of the windows, in severe cases causing the windows to collapse.
Stonework repairs can be costly and it is important to minimise the risk of unnecessary damage but this does not justify doing away with the ferramenta. The easiest solution to conserve the ferramenta is to tip the bars with a non ferrous metal. In the past bronze tips have been riveted to bars, but a better solution is stainless steel welded to the ends using a dissimilar welding process. It is a better solution for two reasons, firstly it is a stronger joint and secondly it gives a more sympathetic appearance.
Restoration
At Fabco we undertake a full restoration process starting with an aluminium bauxite blasting process which removes the corrosion and any residue paint. Then if required we restore any areas of severe corrosion, building up the base metals and sympathetically replacing where necessary. The next stage is to tip the bars with fully certified AISI 316L stainless steel, we use this higher grade of steel because of the various salts contained within the stone. When the tips are added an allowance is made for them to protrude ½” from the stone so that the original base metal does not contact with the stonework. We use a two stage finishing process. The first stage is a corrosion inhibiting zinc coating, the second stage being an oven baked semi-matt black powder coating.
Manufacture
At Fabco we offer a full manufacturing service for new ferramenta using materials such as brass, bronze stainless steel and tipped wrought and black Iron. We can offer various finals (e.g. Fleur de Lys etc.) or we can match existing patterns if desired.
Commonly used Ferramenta in conjunction with historic glass
SADDLE-BAR or TIE-BAR
A bar fixed across the opening of a window, set on the inside or outside, to which panels may be attached by lead ties. Saddle-bars were used either alone or in conjunction with Stanchions.
STANCHION
A vertical support-bar set on the inside or outside (or both) of panels, in order to support them. A stanchion is used in conjunction with Saddle bars which sometimes have eyes through which a stanchion can pass. They were not always required.
T-BAR/LUG-BAR
A horizontal bar set between panels that transfers the weight of the panels to the frame enclosing them. The panels are sometimes held in place by lugs (wedges), in which case the bars are known as lug-bars.
ARMATURE
A framework of metal bars used to hold panels in place. Armatures were used until the late thirteenth century.