What’s in a Window?

Published on 2nd April 2014
They’re simple things, windows. Every house has half a dozen and we’ve been making them for thousands of years, so here at Apropos we thought it only fair that we share some of our knowledge with a handy how-to. Here’s our recipe for making windows.

Firstly, prepare your glass.

You will need the following:


  • Silica sand
  • Sodium carbonate
  • Calcium oxide (or magnesium or aluminium oxide for added strength and durability)
  • Your choice of colorant chemicals – sulphur for yellow tones, lead for green etc..
  • Sodium sulfate, sodium chloride or antimony oxide


  • Large heat-resistant crucible
  • Heat source
  • Glass mould
  • Face mask
  • Heat retardant gloves
  • Metal grasping hooks and poles.


  1. Wearing a face mask, add your silica sand, sodium carbonate and choice of oxide to your crucible. The ratio should be roughly 30 per cent of blended additives to 70 per cent sand.
  2. Add in the colorants – copper oxide creates a gorgeous turquoise hue, iron oxide a calming blue, and nickel is a must for the privacy-hungry, producing darker shades, down to black.
  3. Place over a heat of between 1,500 and 2,500 degrees Celsius. An industrial kiln is an ideal environment, but if you don’t happen to have one handy, see how you get on with your neighbour’s barbeque – be sure to ask permission first.
  4. Wait for the mixture to melt into a liquid form, then stir with a long metal pole to remove bubbles. Add sodium sulfate, sodium chloride or antimony oxide to achieve the desired, sumptuously smooth pouring consistency.
  5. Pour the molten glass into a mould to shape – a large cake tin would suffice, but don’t be tempted to reach for the silicone.
  6. Leave to cool – preferably somewhere dust-free; you don’t want motes in your windows!
  7. Temper the glass to strengthen it and improve durability using much the same method as you would to temper chocolate – heat to between 399 and 538 degrees Celsius and quick cool with blasts of high-pressure air (a bicycle pump or leaf-blower may do if you don’t have anything else to hand).

Next, all you need to do is make your aluminium frame, work out how to fit the glass into the frame while delivering optimum thermal integrity (you could try a combination of putty and Sellotape for that homemade appeal), select the strongest and most secure fittings available, and then install the window into the breezy gap in your home.

Et voila, what could be simpler?

Well, ok, you could just call Apropos and ask us to do it for you… But where’s the fun in that?

For a consultation with one of Apropos’ Design Experts please call: 0800 328 0033 or click here to order a copy of our latest brochure.

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