Gold Ruby glass is a rich red colour and has a history and folk lore all of its own.
The pictures on this page were all taken at Gibraltar Crystal (pictured right), where the master glass blowers Paul Alexander and Stuart Quick were assisted by Joe Flores, Nigel Palao, Harold Romero, and Mack Buttigieg. Gibraltar Crystal has another master glass-blower, Stuart Shut, but he and Daniel Tante (apprentice) were away on the day I visited.
Gold ruby glass is made by including in the glass mixture gold chloride, a solution containing gold produced by dissolving gold metal in Aqua Regia (a mixture of nitric and hydrochloric acid). Tin (as stannic chloride) is sometimes added in tiny amounts to act as a reducing agent, and the process is both difficult and expensive. Today's studio glassmakers can buy their gold ruby glass in rods from specialist manufacturers. This makes it easier for them, but even more expensive.
Most gold ruby glass items made today have a thin layer of gold ruby glass coated with clear crystal.
In this photograph Harold is starting to make a gold ruby vase by taking a small gather of red glass on the end of a punty iron and forming it into shape by rolling it back and forth on a steel marver.
The punty rods, like the hollow metal blowing pipes used later in the process, are about 1.5 metres long.
The Romans made gold ruby glass, and the famous Lycurgus Cup contained both gold and silver. Now in the British Museum, this goblet is red in transmitted light and green in reflected light, and is an exceptional example of the glass-making skills of the Romans, made in the 4th century AD.
Genuine gold ruby glass is obviously an expensive material, and is handled with great care by the glass blowers. In this picture (right) Harold is transferring a small piece of molten gold ruby glass (about the size of a large marble) from the end of his punty iron onto the end of a glass blowing pipe. Joe, holding the blow pipe, cuts off just the right amount with shears.
The apprentices were sharply criticised by Paul if the amount of red glass was too large.
The secret of making red glass was lost for many centuries, and rediscovered during the seventeenth century in Bohemia. At the time this was a blow to the pride and prominence of Venetian glass-makers, who had tried unsuccessfully for years to make red glass.
There was even a movie called "Heart of Gold" made about a village where the secret of making red glass had been lost. 
I have never seen it, but have been told it is very good.
There is a myth about the discovery of a formula for red glass, that someone dropped a gold ring into a vat of molten glass and it turned red. This is unlikely to be true, as experiments have shown that all you would get is a puddle of molten gold at the bottom of the unchanged pot of molten glass. The gold has to be chemically treated before adding it to the glass mixture.
This photograph shows the next stage in making our red vase. The blowing pipe is handed to the master glass blower, who blows the tiny piece into a small bulb, and then dips it into the furnace containing a pot of molten clear barium crystal glass, gathering up a large coating of clear glass over the red.
Barium crystal is an improved substitute for lead crystal, with a higher refractive index than 24% lead, similar weight, and the same coefficient of expansion as the coloured glass. This makes for fewer failures at the annealing (cooling) stage, since glass with differing coefficients cool at a different pace and are likely to fracture.
Paul works this ball of glass on the end of the blowing iron, keeping the rod moving backwards and forwards all the time, otherwise the molten glass would droop downwards and the piece would be spoiled.
He is using a (traditional) wad of wet newspaper to work the glass into an even shape. Notice the bucket of water at his side, and the wooden arms to the chair, so that the rod can be kept rolling all the time. You can see the glowing orange colour of the molten clear crystal glass, and at its centre, the ball of gold ruby glass. 
Cranberry glass is another type of red glass made from gold, but the colour is paler (usually a delicate pink) because there is less gold chloride in cranberry glass than in gold ruby glass.
Once he is satisfied with the shape, Paul takes the rod with its gather of molten glass and swings and blows it to a slightly larger size, then plunges it into a steel cage of vertical ribs (picture right) to give the vase what is called an "optic" effect, or a ribbed surface.
Johann Kunckel is usually credited with re-discovering how to make gold ruby glass, in Brandenburg, Bohemia around 1670. He was a chemist from a glass-making family who published the results of his experiments in a famous book "Ars Vetraria Experimentalis" in 1679. Others who are sometimes named as the inventors of gold ruby glass are Andreas Cassius (whose purple-red pigment called "Purple of Cassius" was very hard to make and was sometimes used to colour glass red) and the German chemist Johann R Glauber.
The next stage in making our vase involves placing the glass into a mold, which is then closed by an apprentice, as shown in the photograph (below).
Paul blows the glass into the mold, whilst turning it all the time. This gives the vase the shape of the mould, and depending on how much turning, can also give the optic ribs a twist.
You can see that he is standing on quite a high step so that he can blow down the very long pipe from above whilst the vase is held in the mold placed on the floor.
In the picture on the left, Mack has just opened the mold after the vase has been blown to shape. You can see the long handles attached to the two hinged pieces of the mold.
The master glass-blower then works the piece backwards and forwards whilst sitting in his "gaffer's chair", making sure the shape is right and preparing the neck so that it will break away easily from the blow pipe.
The next stage is to attach a pontil iron by means of a blob of molten glass, onto the base of the vase. Paul takes hold of the end of the pontil iron with his tongs to bring it into contact with the vase, whilst Stuart, 
holding the iron, must keep it aligned.
The reason for attaching the pontil iron is that the neck of the vase still needs to be finished, and will require re-heating in the furnace to keep it workable.
There are other chemicals which produce red glass, but none which have the special magic of gold ruby. Most red and pink glass today and for many years past is made from selenium.
Frederick Carder (at Steuben Glass Works, USA) invented a brilliant red glass by incorporating cadmium selenide and zinc sulphide in the mixture. Cadmium sulphide glass, which is yellow, changes to orange when selenium is added, and to bright ruby red if sufficient selenium is put in.
The Egyptians used copper to produce red glass (which was opaque) but making red glass using copper is an extremely difficult process. Since 1832 copper has been used as surface stain on glass to produce red colouring.
Returning to our gold ruby vase, having connected the new rod, a sharp tap with a knife on the blowing pipe is enough to separate the glass, and leave the mouth of the vase ready for finishing.
Stuart then presents the vase into the "glory hole" (a small furnace or a small entrance to a furnace) to melt the top (as it will have cooled during the earlier processes). You can see that the size of the furnace mouth has been reduced by placing a mask over the entrance,
and this is held in place with furnace bricks and a metal frame. The reason for this is that it saves heat loss when there is no need for a large access point. Compare this to the furnace door used by Gary Nash for the same purpose (http://www/glass.co.nz/nash.htm)
Stuart then uses his tools (in this case a wooden spatula) to form the shape of the vase top.
When he is satisfied, he hands the completed vase on the punty iron to an apprentice who places it lip down on a bench and with a sharp tap disconnects the punty iron.
The studio crest, shown below, is then stamped onto the base, and the vase is gently lifted into an annealing oven, where it gradually cools down over a 24 hour period.
This slow cooling is essential to make sure the glass does not fracture due to different parts cooling at different rates. 
And the final result is this beautiful gold ruby vase on the right.
The crest of Gibraltar Crystal is the coat of arms of the city of Gibraltar. The studio was set up only two years ago, sponsored by the Department of Tourism. Both Paul Alexander and Stuart Quick came from the Dartington Glassworks in England to found this studio and train local apprentices. Paul has over twenty years experience in glassworks management, and Stuart worked at Dartington for twenty five years.
Another of the specialities made at Gibraltar Crystal is a form of Graal glass, which uses the skills of their engraver, Donna Macleod. And last but not least Paul would like to mention the other member of their team, packer, Johan Martinez. We leave you with two more images of glass made at Gibraltar Crystal, a collection of their ruby glassware, and a beautiful pink vase with pulled trails.
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