BlogRenovating iron window frames

Renovating iron window frames

I have recently carried out some work for a client who lives in an old converted mill. The property is listed and lots of original features are still present, including many iron window frames.

Restoring these type of windows is very time consuming as they have often been neglected for many years due to the amount of work involved to restore them to their former glory!

There were several issues with the windows. A lot of the old putty was either missing or so perished that it would need to be removed. Rust was also an issue as the areas of bare metal had become wet from condensation leading to rust over much of the surface. Some of the panes were either cracked or broken and of course these need replacing.

iron window frames

iron window frames

It takes time and patience to do a comprehensive job and I had allowed a little under three days per window.

As I was in for the long haul so to speak, effectively three days standing in the same place I needed some essential items. A dust sheet to spread any tools and consumables items on for easy access, some bright LED lights and a radio, mostly tuned to BBC2 !

Initially I needed to remove all the loose paint and defective glazing putty. Some safety items were needed. Gloves as I would be using sharp blades and working around rough metal and safety glasses to stop any bits flicking into my eyes.

the tools

removing defective material

removing defective material

To remove all the defective material I used a combination of knives, specifically an Olfa BTC1 with its dedicated blade. These are effectively like using a very rigid single edge razor blade in an ergonomic handle. I also use an Olfa L5AL, however I decided to use some other standard blades in this which are non segmented. This is because I knew I would be applying quite a lot of pressure and the segmented blades can break.

Another useful tool is my plastic hammer which I used in conjunction with an old wood chisel to remove any putty which seemed well adhered but appeared defective. The advantage of the plastic hammer is that it is easier to control when working next to fragile glass.Any panes which were broken had all the putty removed so that the remaining broken glass could be safely removed. I tend to apply masking tape on the broken glass and then tap it to break it up. The tape means that the shards tend to stay together (well mostly!)

plastic hammer

Having removed all the loose putty and flaky old paint I was faced with what I would probably call a mess! Rough rusty metal frames. I used my extractor to suck up all the detritus from raking out the old putty. I also passed the extractor hose over the frames to remove any residual loose bits.Essentially all the metal work and any remaining putty needed abrading well to remove loose surface rust and any remaining loose paints on the putty. To do this I used a piece of 120 grit Abranet and some 150 grit Mirka Goldflex. All the sanding was carried out manually and where excessive dust was appearing I wore a mask. Once I was happy that there wasn't any more defective material left behind I once again used the extractor to remove all the dust from each pane. I wanted to be sure the surfaces were clean so with a Microfibre cloth and some Meths I cleaned all the rusty glazing bars and any remaining putty. I also cleaned all the glass with a clean cloth and Meths.


dust mask

cleaning products

I made some templates from pieces of paper for the replacement glazing and sourced the new 2mm thick glass from a local glazing specialist.

Applying a rust inhibitive primer is essential to help prevent the rust coming through the new sealants and paints. I chose to use Rustoleam 3380 primer in grey. Its quick drying and sticks very well to rust. I applied two coats for extra security with an Axus sash brush.


Glazing putty is an old fashioned product which takes too long to cure before it can be painted so I chose Graft MS Polymer. This is a modified silicone which is very flexible, dries quickly and is over paintable. It bonds to many substrates including glass so I also used it to set the new glass into the rebate. I applied a small bead to the edge of the glass and gently pressed it into the surrounding aperture.

Now for the tedious part! Masking!


As the panes were small and I decided to apply three coats of paint it was more effective to mask each pane. It speeds up application of paint and also means all the paint lines are pin sharp and also line up with adjacent paint lines on other panes of glass. Also as I was using Graft MS Polymer to seal the glazing it was imperative to mask the glass to get the sealant neat and tidy. I used 3M Blue exterior tape with a one inch width. There were several reasons for this. It has good adhesion and clean removal without leaving other bits of tape behind. There is minimal risk of paint bleeding behind it and it is also waterproof to an extent so if any condensation appeared over night it would not affect the tape. I usually apply a dozen or so bits of tape leaving them longer than necessary and then trim each one with an Olfa blade while keeping the cut line straight with either another window scraper blade or a two inch filling knife.

I loaded the tube of Graft MS into my sealant gun and liberally applied the product in the gap between the glazing bar and the masking tape. I used a few different rubber silicone tools to smooth the sealant into the gap and made sure there was no significant thickness of sealant on the masking tape. This is because I wanted to be sure there was paint on a couple of mm of glass to form a bond and also a sharp line when the tape is removed. I had a tub of industrial wipes to hand and used several on each pane to remove excess Graft from my silicone applicator tools.


The Graft MS was left to dry overnight.

I decided to use Zinnser Coverstain as my primer undercoat as it sticks to most surfaces. I added some Owatrol paint conditioner to the paint as it improves flow and also acts as an extra rust inhibitor on any bare metal.The undercoat was allowed to dry. In this case I left it over night as it had been applied to the Graft which is quite rubbery so drying can take a little longer.



For extra durability I used an oil based gloss for the two top coats. In this instance I specified Dulux. I don't use Dulux products so much now for a number of reasons but still find their oil based gloss good, and it was also the correct colour for the clients specification.

After the two coats had been applied and before they had dried I carefully removed all the masking tape. I now wear disposable gloves for applying and handling any oil based paints. This is mainly because it is hard to clean off your hands without the use of solvents and when the gloves become contaminated its quick to put on a clean pair.

After the paint had dried properly I gave the windows a clean with some water and a micro fibre cloth.


The client was extremely happy with the final result as the old deteriorated frames looked shabby in a character property. The newly renovated windows really did transform the room.

  • Recommend:
  • Share: