Cast iron window glazing question

[TOV1]

Hello,
I'm new here, having recently moved our new period home. The outbuildings have the original cast iron windows in situ. One is mostly glazed and original but four others are already stripped back and zinced ? (they have a red surface to them). The four all need re-glazing and I am trying to find out the best way to do it...or who to ask if its beyond me. They are all fixed in the wall so I am thinking they will need glazing in place. Do I need to paint first? Do I use normal putty or a modern piped version - I feel like normal putty would provide more control... glass or acrylic? Can anyone offer any advice please? Thanks

 

[Cubist]

A word of caution; cast iron can be very delicate and easy to fracture. Extreme caution needs to be exercised when removing any hard deposits such old putty or rust scabs - particularly in cold weather - and no part of them should be struck with say a hammer or a chisel.

It's feasible though that these are steel rather than cast iron. Some close up photos of the corners of the glazed areas, both internally and externally, would provide good clues insofar that steel would have been either forge or electro welded while cast iron would show no such evidence - but casting marks may be revealed in these and other locations.

Zinc paint coatings are typically a silver grey in colour. The red coating you are seeing is more likely to be a red-oxide primer commonly used for the protection of the base metal and preparation for other - typically black, finishing paint colours. Care should be exercised when choosing such final paint finishes as many intended for use on metals are intended to produce a 'hammered' finish- such paints while appropriate for the metal do not work well over putty and similar glazing products.

Fortunately you have an opportunity to measure the thickness of some of the glass. If sub 4mm then this is likely to be thin glass typically used today in picture frames but was frequently used in the past for decorative, often stained, glass. It too is extremely delicate and needs careful handling at all times. Such glass is still available and, while you might consider using a thicker, say 4mm, glass to replace the lost panes you should not consider using acrylic products - this material would be obvious and will clash badly with the old glass.

The metal frames must the carefully cleaned back to remove all old paint coatings, if any, and to remove as much rust as possible. The exposed metal can then be painted with a red oxide as some already have and then painted with your chosen final finish BEFORE any new glass is installed - it is important to clean out any old putty from the glass seating areas and paint these to inhibit future rusting.

Traditional putty would be the best product to seat and close the new glass. A little practice will be needed if you intend to DIY the job but an experienced glazier would make short work of the job to produce a satisfactory finish. You will of course then need to paint over the putty, once it has dried sufficiently, with your chosen colour to form the final seal over the putty, the glass and the frame.