It is difficult to briefly explain each and every of the operations – sometimes very laborious and complex ones – that each of the processes they carry out entails. However, the manufacturing procedure basically has the same phases for all the leaded stained glass windows… they develop. These are detailed below.

1. Design of the window. The idea behind the chosen design is first materialized at a reduced scale elaborating a draft, which, once it is approved, will be the basis to carry out the so-called cartón or real-size draft. This second draft will be then cut out using double-edged scissors to obtain the templates for each of the pieces which will make up the final stained glass window. 

2. Cutting of the glass. Once the templates are ready, these are placed on top of the selected coloured glass, cutting the pieces using a special blade. Once these pieces are cut, they double check the pieces to ensure they coincide with the original idea and that the measurements of each of them are correct. 

3. If the stained glass must be painted after, in order to obtain a greater feeling of depth and volume, each one of the pieces will receive a coating of vitrifying sands and enamels and then will go into an electric oven (muffle oven) where they will be fired at a temperature between 700º and 800º. This kind of electric oven does not generate any sort of fumes nor excessive noise.

4. After the firing of all the pieces – or with all the pieces cut to their adequate size if we have skipped step C – the next step involves the use of lead. The process of leading up is carried out placing a lead ingot along the main piece. Once on the working surface, the way to proceed is to continue incorporating lead rods and glass pieces until the stained glass window is complete.

5. When all the pieces have been leaded, then the unions are welded with tin. 

6. Lastly, with a bristle brush, a special type of caulking is applied. This caulking is made of powdered calcium carbonate and linseed oil and is important for it to penetrate within the joints between the lead elements and the glass. Once dry it acts as an elastic seal which will absorb the thermal expansion and shrinkage of the elements and the possible vibrations which can also occur. 

In the restoration of artistic stained glass windows several factors are important to be considered: the specific location where it is going to be placed, the type of stained glass window on which the actions are going to be carried out, the antiquity of the element and the historic or artistic value of the piece, etc. However, there are always a series of operations that will be carried out:

Obtainment of pictures and labelling of panels for their later identification. 

Removal of panels from their original location and transport of the panels to the workshop. 

Placing of provisional glass pieces to substitute others (if necessary).

General cleaning with neutral detergents and non-abrasive means which guarantee the permanence of original vitrified paint, eliminating accumulated dirt.

Replacement of broken pieces which present compound fractures. Those which present simple fractures which do not affect the aesthetics or the security of the stained glass will be maintained to preserve the greatest possible amount of original pieces.

Re-leading up of the most affected parts of the window using velgas (kind of lead rods) of the same calibre as the original ones.

Going through all the metal and glass joints and re-welding them.

Caulking of the piece with fluid caulk made of calcium carbonate and linseed oil.

Transport to the site and placement on site.

The necessary tools to carry out these actions are detailed below:

Cutting tools: story poles, flat surface pliers, special pliers to open the cut of the glass, double-edged scissors, simple scissors, squadron, blades.

Tools for welding: welding torch, solder paste, tin, heat-testing can.

Tools for leading up: sharp scraper, knife to eliminate burrs, hooks to work with lead, nails, hammers, pliers. 

Tools for painting: paint brushes and brushes, scrapers, quill, maulstick, palette, vitrifying sands, enamels.