VISIT US Bergdala glastekniska museum

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- The processes from an environmental perspective
- Environmental problems, history and future
- Why "Kingdom of crystal"?

The glass industry, why did it become an environmental villain?

From the raw materials to the finished glass

  1. The first step is to melt the batch, a mixture of sand, melting temperature about 2000 degrees, soda, melting temperature 850 degrees and lime, 825 degrees.
  2. Then you want to use different methods to process the soft, semi-liquid glass. During processing, it has about the same consistency as syrup.
  3. The third step is to cool down the object slow enough to avoid internal tensions that can cause it to crack or even explode.
  4. The final step is (possibly) a cold decoration or finishing. Such processes include grinding, etching, sandblasting, painting and others.

Making the batch

The mixture of sand, soda and lime is called "the batch". Until about the 1970s it was very common that the individual glasswork stored, crushed, milled and mixed the raw materials themselves. If you turn around you see a loading dock at the glasswork gable. That was where the sand and all the other raw materials for the batch was received at Bergdala glasswork.

For a proper melting process must all the ingredients be ground to a very fine grain and the mixing must be homogeneous. Therefore, there was not only containers for different materials, but also crushers and mills and rotating vessels, mixers. You might be able to imagine how dusty this handling became as the dry materials were crushed, milled and mixed. And the batch would often contain also lead or arsenic or ... The dust containing these substances would not stay indoors but would spread to the surrounding atmosphere and land on the ground around the glassworks.

Not to mention the working environment.

Nowadays it is very unusual for a small glasswork to make its own batch from the raw materials. Instead they would buy ready-mixed pellets from companies who specialize in developing recipes for glasses with special properties. The pellets look like small balls with a diameter of a few millimeters. Before delivery the pellets are also sieved to remove the smallest particles. Because of this the dusting and emissions to the environment during the making of the batch has been radically reduced. Meanwhile, the working conditions inside the glassworks also become much better.

The companies producing the pellets have to meet high demands in terms of dust emissions. But since they are specialists at handling hazardous powders of various kinds, they are also specialists in preventing emissions.

From this background you will understand that here, at Bergdala glasswork, where the batch was produced manually during 80-90 years, there is lots of heavy metals and poisonous dust in the soil around the factory building.

batch making in the 1950-ies

loading for melting in the 1950-ies

Melting the batch

During melting, gases are released and they will form bubbles in the glass melt. In most cases you do not want to have bubbles in the finished glass. Therefore, one must ensure that the glass during the melting process is so fluid that the bubbles can rise to the surface and disappear. Moreover, one has to wait long enough before starting to work with the glass so that all bubbles have really had the time to disappear. This is called "plaining" or "(re-)fining" and you can add special fining agents to make it extra easy for the bubbles to bubble up through the melt and disappear.

Again to shorten the plaining time you would usually keep an extra-high temperature during fining. Just like the oil in the frying pan becomes less and less viscous the warmer it is, also the glass becomes more and more fluid as the temperature rises. Therefore you would typically keep the temperature around or over 200 degrees higher than the working temperature. So if you want the glass at 1100 oC for blowing the refining temperature would probably be at 1300-1350 degrees. For certain glass qualities it can be as high as above 1500 degrees.

At such high temperatures, a lot of substances evaporate. The gases leaving the glass furnace and eventually ending up in the chimney will then contain some unhealthy substances. If there is lead in the glass, some of the lead is vaporized and comes out the chimney. The same applies to arsenic, antimony, and lots of other substances added to give the glass the desired properties.

When the gas then cools during passage through the chimney, several of these substances condense again and fall down like a fine dust in the vicinity of the mill. The dust is so fine as to be invisible.

Huge efforts are put into finding substitute materials to the most dangerous and hazardous additives, substitutes with less toxicity but that can still give the glass the same quality and properties as the old additives could.

Today many glass melting furnaces are electric so there are no combustion gases and temperature control is better than it used to be. In combination with the pre-manufactured pellet-batch this has radically reduced the total emissions from the glass melting process itself. But one has to accept that in the area surrounding a historic glass work as Bergdala, more than 120 years of operation have accumulated to quite a lot of kilograms of hazardous substances.

The hot working

Manual glass blowing is touristic, spectacular and is one major reason that tourists come here at all. At larger glassworks you will be able to see how a team, a production shop, of up to five persons or so, each and every one being a specialist. The master ("gaffer")will be the one doing the most complicated or sensitive operations.

The temperature in the furnace will be lower than it was during smelting and refining, but a small part of the additives will still be vaporized during this phase.

Thus a minute portion of glass will be lost in the form of gas, simply because it is so very hot. As the gas cools down these substances will condense to form a microscopic dust that remains near the mill. From the pipes, glass remnants are sheared off, and this, together with cutoffs and others fall into the water in buckets and tubs and other collectors in the workshop.

Water is an amazing substance. Water can dissolve almost anything, iron and copper, gold and silver. But some substances, such as glass, dissolve only very slowly. So if there is a very fine-grained dust of glass on the ground around the glasswork, then will rain water slowly dissolve the glass, and then the dangerous additives enter into the ground water. The smaller the dust particles - the faster the dissolution.

Around each and every glasswork that has been in operation for more than a hundred years, there is such a fine glass dust in the ground. Some originates from the handling of the pulverized batch, some has come through the chimney and some has come out through doors and windows. Therefore, you should be a little extra careful when staying on or playing around glassworks.
This applies at all glassworks and, indeed, it applies at all other process industries too!

the beginning of a pitcher (1950-ies)

Cold working and finishing

When a glass piece - whatever it is, almost - has been completed in the "hot shop" and has been cooled down in the annealing oven is the time to smooth the edges, for planar grinding, grinding off the navel (punty marks?) and the like.
The grinding dust is much coarser than that formed as gases emitted from the hot glass condensed, so this dust falls down even closer.

Because this dust is quite coarse, it will dissolve very slowly but on the other hand it can be quite a lot. Grinding off the navel from a plain drinking glass may require the removal of a whole gram of glass before the bottom has become smooth and stylish. Then it becomes quite easy to figure out how much glass dust you'll get in an hour or a day or a year.
Some of the more magnificent pieces of crystal can be cut in a very deep pattern, and then you can try to imagine how much glass has actually been transformed into a fine dust.

On spun, cast or pressed glass you normally do not grind away as much as from blown glass. Some products may require no grinding at all.

grinding the edge of a glass (1950-ies)

Remnants, cut-offs, breakages

Especially during hot working glass residues are formed. The blow-pipes are cleaned from old glass before new melt is gathered, edges are cut etcetera. Whenever possible, different colours are kept separate so that it will be easy to reuse the glass, but this is not always possible. Moreover, there are always some breakages that must be discarded.

At every glasswork there is a glass dump, the place where shards of mixed colors as well as melting residues, shear-offs and the like have been thrown. It is only the last few decades that it has become a routine to collect all the glass waste in containers and take care of it in a professional manner.

In the dumps you will find sharp shards, broken glass, also such pieces of glass that are just discarded for one reason or another, bad colour glass perhaps leaking toxic additives because melting or any other step in the process went wrong, and things that cannot be reused because they have mixed colors, or...

Here - in Bergdala - the glass dump has received scrap glass since 1889 until the late 1900's. A bit more than one hundred years.
It's not surprising that the total amount is significant ant that the exact location for all this scrap is not known, is it?

The fenced area behind here does have a margin but you must always remember that the soil and the water around a glasswork will always be contaminated.

the edge of a pitcher is cut off (1950-ies)

But what is done to fix the environmental probems today? Read more on the page Environmental problems, history and future!

The pictures in the right-hand column come from a series of photos from Orrefors (probably late 1950ies). We have the whole serie published here. (One of these days it will be viewable from here, too...)