What temperature is the glass?
- The glass in the melting furnace is 1.110°C - and it is workable until it reaches approx. 850°C
What do you use for heating the furnaces?
- The melting furnace and the glory hole (furnace for re-heating only) are fired with propane gas and the annealing oven is electrically heated
What is glass made of?
- Glass is basically a mixture of quartz, soda and lime. Modern glass also contains a number of additives to obtain the specific characteristics one needs - transparency, time to manipulate the shape, compatibility towards colours etc. To obtain a sufficiently uniform glassmass from day to day, we buy our glass from a factory in Sweden.
Glass is an amorphous material, which means that it in fact is a fluid - it is said to move, very slowly of course, even in its cooled stage.
How do you add colour to the glass, and what is
it made of?
- The glass in the melting furnace has no colour, so if we use colour we have to add it after taking the glass from the crucible. Normally the colour lies in a very thin layer. For the smaller items we produce, we primarily use colour powder rolled on the outer surface of the glass. We also use underlay colour, concentrated colour delivered in rods. One preheats a piece of colour rod and picks it up with a glowing hot blowpipe. It is then heated up further and a small amount of air is blown into it. After cooling it down somewhat, one gathers a layer of clear glass over the colour. This is repeated several times, until the desired amount of glass is gathered. Additional colour is eventually added between the layers to create various decoration effects.
Glass colour mostly consists of glass with various amounts of metal oxides and, therefore, reacts very differently towards the heat, therefore some colours gain/lose temperature very quickly - others react slower
Where is the glass?
- The glass is inside the melting furnace in a ceramic crucible, and has the consistency of warm syrup. Therefore it takes quite a lot of practice to gather and position the right amount on a blowpipe or a gathering iron
Do you turn off the melting furnace when you go
home after work?
- No, the crucible would become very stressed by the great temperature deviations that would occur and besides, it would be too costly to reheat the furnace every day. In fact, it takes approx. 2 days to cool down or heat up the furnace as it has to be done very slowly, therefore, so we try to restrict this to a couple of times a year
What is happening in the "cupboard" where
you put the glass after you finish it?
- After finishing a piece of glass, it has to be annealed properly. It is essential that the glass is cooled down very slowly, so that the temperature remains the same inside the glass and on the surface, all the way down to room temperature.
Our annealing oven is kept at approx. 485°C during the day. Once the production of the day is done, the oven is turned off. Its thick stone walls emits the accumulated heat very slowly, so that we can take out the production with our bare hands the next morning
Do you need "big" lungs?
- No, blowing glass is first of all a question of timing - and to make the most of the heat while it is there
Do you get burned often
- and does it still hurt?
- We burn ourselves frequently, but hardly ever on the glass. When we burn ourselves, it is usually on the tools, for example the legs of the shears that are lubricated with a mixture of wax and lampblack. Glassblowers usually have small scars on the thin skin of the forearm - and yes, it still hurts every time we burn ourselves!
Do you know what the end result will become when
you start on something?
- Yes, at the beginning of the day we have already planned what has to be made during the day. When one makes glass, the working process has to be carefully planned, and the rhythm and all the processes in making a particular piece of glass have to be optimized. It looks very relaxed and easy to make glass, but every little part of the process has great significance. Making glass takes a lot of concentration, focus and good team work. It is essential to utilize the time efficiently, since it is very costly to keep a glass workshop running.
When do you blow?
- Blowing is not always the most interesting about making glass. For example, the blowing of a candlestick is quickly done. After blowing, one has to draw the stem, make a foot etc. - all details that are equally interesting to watch
How does one become a glass artist?
- There is more than one answer to that question. Some attend the Orrefors Glass School in Sweden, some go to the UK to attend one of the art-schools teaching glass there. In Denmark, we have Glas og Keramikskolen paa Bornholm. They offer a 3 year advanced course in studioglass. A good (and inexpensive) opportunity to explore glassblowing, before committing oneself to a long term education, is to attend a Danish "hoejskole". As an example, good courses are held at Engelsholm Hoejskole of different durations.
Do you manage to keep warm? (ha ha)
- Yes, thanks for asking - we only freeze in our leisure time