Whether you want to replace cracked window putty, need to replace a broken window pane or have new windows to glaze, working with putty is simple with a little know-how
By Gina Hartoog
Are your windows properly sealed? Can you feel cold air if your place your hand against the sides of the pane on a cold evening? The window putty may be dry and cracked, leaving the glass unstable in the frame. You can remove the old putty and replace it even with the glass in the frame.
It is always best to remove and replace all the putty around the frame and avoid a bits and pieces patch-up job. You can also use the opportunity to replace a cracked glass pane.
What is window putty?
Rouke Shirley of Powafix:
Window putty is a blend of natural oils, oxides and a limestone based powder. These are blended together very carefully to give a slightly oily, malleable product with a pleasant low natural odour.
This formulation of putty is suitable for glazing in particular, but is also used as a filler and sealer, particularly in the plumbing trade when fitting toilets to the sewer system. There are other putties available that have additional additives that can make them heat resistant for use in fireplaces, pizza ovens and other applications where heat is present.
Powafix putty is supplied in two colour variants: White and teak.
Teak putty contains an oxide to darken it to a similar colour as that of meranti and can be used on wooden window frames that will be varnished.
White putty, on the other hand, does not contain any oxides and is suitable for any application that will be painted over. Coloured oxides can be mixed with white putty to achieve a desired colour. Raw linseed oil must also be added to keep the putty malleable.
Never add paraffin to the putty to speed up the drying time as this will cause it to crack over time.
Remove glass safely
Safety always comes first when working with glass. Make sure you have good quality work gloves and eye protection before attempting to remove a pane of glass. Pets and children should be well out of the way.
* Cover the pane with a suitable broad tape or use plastic sheeting for large windows. Leave the sides open so you can get to the putty.
* Use a hammer and gently tap the glass to break it into smaller pieces. The tape or plastic will hold the glass in place and prevent a mess.
Steel window frame painting tips
Before you start painting a window frame, it is important to consider that a window has two sides – the interior and the exterior. This is very important. Should the interior colour differ from the exterior colour when the window is opened, what areas of the window do you see from the interior and then also the exterior?
The best solution for restoring steel window frames, especially those that are showing signs of rust underneath the paint, is to strip them down and start from scratch. To achieve best results, window frames must be painted in a certain order: Glazing bars, top and bottom horizontal bars, inside verticals bars, outside edges and outside frame.
* Open the window as wide as possible.
* Properly safety precautions must be followed. Pant strippers are dangerous, so use goggles, plastic gloves, a long sleeve shirt or overall and lots of ventilation.
* Place drop sheets on the sill and floor area.
* Apply the paint stripper liberally, working from the top of the window frame to the sill area. Paint it on with a brush.
* Don’t rush it, give the stripper time to work, but do not let it dry. Read the instructions on the container. Less time will be needed for the actual removal of the paint sludge.
* Scrape off the paint onto newspaper using a paint scraper.
* With many layers of paint, more stripper needs to be applied.
* Clean off the loose paint residue using a water soluble degreaser, for example, Polycell Brush Cleaner, and a scouring pad.
* Rusty areas must be treated with a suitable rust inhibitor or primer.
* Apply one sufficient coat of universal undercoat and allow to dry for 24 hours.
* Apply two final coats of an oil-based gloss enamel, allowing 16-24 hours drying time between coats or two coats of water-based gloss enamel allowing 6-8 hours between coats.
* The inside window frames get a bit grubby over the year due to condensation and dust. They can also be infected with mould growth. Treat the mould with a solution of bleach. Dilute 5:1 with water.
* Unscrew handles and other brass attachments on the window frame before stripping and painting.
*Fill the gap (between the frame and the glass) with a paintable flexible acrylic sealant. It stops rattling window panes and is easy to paint over.
* Sand down the painted surfaces with a 120-grit sandpaper to give key for the undercoat and finish coat. Allow to dry for 16-24 hours.
* Finally apply one or two coats of the final topcoats. Oil-based paint must dry for 16-24 hours between coats and water-based gloss must dry for 6-8 hours between coats.
Information by Tony Stella, email:
How to re-glaze a window
Step 1: Assemble your tools
You will need a hammer, putty knife, putty for a wood or steel frame, linseed oil and mineral turpentine. About 500g of putty will glaze approximately 1m of frame
Step 2: Remove old putty
Using a putty knife and hammer, remove the putty and any remaining glass (see box). The old putty can be tapped out. Ensure all old putty, dust and loose particles are removed from the frame. Never use a screwdriver on a wooden frame as it will damage your frame.
Step 3: Prepare the frame
For wooden windows, apply a coat of raw linseed oil to the frame. This will prevent the oil in the putty from being pulled into the wood, causing it to dry out too quickly and crack. For steel frames, treat any exposed metal with a suitable metal primer. For new windows, make sure that all traces of cement and dust are removed from the frame.
Step 4: Prepare the puttyWork the putty by hand to make it smooth. Add a little linseed oil to soften it or leave it in the sun while you take out the glass.
Step 5: Putty the windowApply a thin bead (like a rope) of putty to the window recess – use your thumbs, it makes it easier. Shape and smooth with a putty knife. If the putty is a little sticky, dip the knife in turpentine.
Step 6: Install the glassPress the glass pane firmly but gently into the putty. Always press along the sides into the putty, never in the centre of the glass.
Step 7: Outside puttyApply more putty to the outside of the glass. Use a putty knife to shape the 45̊ angle at the corners of the windowpane so that the putty slopes from the glass down to the frame.
Step 8: Drying and painting
Putty takes between seven to 14 days to dry. Leave it to dry completely before painting. Clean the window with a suitable cleaning solvent. Do not leave the putty unpainted for longer than 17 days. See the box for painting steel windows frames.
For wood, apply a few coats of varnish to the frame and putty. Allow to dry properly between coats.
Sources: Additional information: Rorke Shirley, Powafix
Apply masking tape to the window before you tap the glass to break it. This will help to hold the glass in place and contain the mess
Professional glazers may be able to cut glass to shape on site, but if you are not experienced in glass cutting, rather take a template to the glass merchant and have them cut the glass to the correct shape
Window frames must be clean and free of debris
Work the putty with your hands to soften it a little
Apply the putty to the recess in the window frame
Carefully push the glass into place at the sides
Apply the outside putty layer
Use a putty knife to remove excess putty and create a smooth 45̊ angle