German Glass Industry Report 07 on

German Glass Industry 48 After September 1945


  Target No.
Map Ref.
Name of Target Deutsche Spiegelglas A.G. Werk Mitterteich
Address Mitterteich, Oberpfalz, Bavaria.
Date of Visit 23rd August, 1945
Products Spectacle glass principally.

Coloured glasses, including various filter glasses (e.g. ultra-violet absorbing) and Signal glass.

Clock and watch glasses, lens blanks. During the war colourless glass 2-40 mm. substance was made, the thickest being sent to Jena for moulding into tank periscope prisms; it was not known whether thinner substances had been used for laminating for war purposes.

Present Position Production stopped in April, 1945

Bomb damage was superficial to buildings and this had been repaired. Production could be restarted with 700 tons coal per month although normally 2,500 tons were consumed per month. Raw material stocks, with the exception of soda, are good for a few months.

Key Personnel Dr. Gerhardt Schott, the Chairman of the firm, was at the Head Office at Grünenplan, near Alfeld a.d. Leine, Hannover.

Works Manager - Theordor Heyser
Sales Manager - Georg Neff

This factory belongs to the same Company as the factory at Grünenplan. The two factories have, therefore, much in common. One major distinction is, however, that whilst at Grünenplan watch glasses are blown from glass gathered from the spectacle tank, Mitterteich is equipped with a separate small tank for this type of glass.

Furnaces, etc. One Tank with 1 Fourcault machine 1.2 m. wide.
One small experimental tank with a small Fourcault machine.
One tank for producing blown clock and watch glasses.
Eight pot furnaces (totalling 42 sieges) Twenty bending kilns.
German Glass Industry 49 After September 1945
Employees Pre-war
During war

Description of Plant, Processes, etc.

1. Gas Supply

There are four “Demag” static producers with automatic ash removal. Coal was fed into a gas tight bell from overhead bunkers. Top poking was done by hand. The blast was fed through ordinary type blowers at a temperature of 50°C. to 54°C. Each producer could gasify 25 tons per day. Three were worked with one in reserve, though the flues contained sumps to collect tar. For the quality of the glass produced it was only possible to utilise coal from Bohemia because of its low sulphur content.

Composition of Gas: CO2 4.3  
  CO 27.8  
  CH4 3.4 combustible 49.2%
  H2 18.0  
  N2 46.5  
Calorific Value 1,645 Calories per cubic metre

2. Mixing Room

All the materials were housed in closed wooden bins along one side of the room and were all weighed on the same weighing machine giving direct weight before mixing in a “Saxonia” type mixer. This type of mixer has already been described in the report on the Weiden Works, (q.v.) Eight or nine revolutions of the mixer were sufficient for each batch.

Composition of batch for producing Tank Spectacle Glass and Tank Watch Glass:
  Sand (Dörentrup or Lippe) 100 Kg  
  Limestone 28 Kg  
  Soda Ash 22 Kg  
  Sodium nitrate 2 Kg  
  Potassium Carbonate 16 Kg  
  Barium Carbonate 5 Kg  

It was stated during the visit that an attempt is to be made, when

German Glass Industry 50 After September 1945

production restarts, to decolourise the glass with Antimony.

3. Tanks

Fourcault Tank - Spectacle Manufacture

Capacity: 50 tons Load: 8 tons per day
Dimensions: Length 7 m.
  Width 3.5 m.
  Depth 0.8 m.

The tank had a bridge wall with a central doghole the dimensions of which were 1 m. wide and 40 cm. high. The melting end was cross-fired. The gas and air, after regeneration, were fed through two stacks to seven small ports - four on the 1st stack and three on the 2nd stack. All the blocks used were chamotte from Didier Werke.

The crown consisted of a flat arch, and each block was suspended separately. There were two stacks each side at the working end in which the air was recuperated and the gas fed direct into the stack neck.

The width of sheet was 1.2 m., drawn at the following speeds:-

2 mm. thickness at 1.5 m. in 3œ min. (17 in./min.)
8 mm. " at 1.5 m. in 6 min. (l0 in./min.)
14 mm. " at 1.5 m. in 10 min. ( 6 in./min.)
  Temperatures: Melting end 1,520°C. (crown couples)
Working end 1,100°C.

Filling was done by hand.

The tank bottom and sides were renewed every 10 months.

Blown Tank - Watch and Clock glass manufacture

Capacity: 7 tons Load: 2.5 - 3.0 tons
per 24. hours.
Dimensions: Length 5 metres (16œ ft.)
  Width 2 metres ( 6œ ft.)
  Depth 60 cm. (2 ft.)

Filling was done by hand into the filling pocket on the side of the tank which was of the open hearth type fired with a horse-shoe flame from the front wall and was built with chamotte blocks from Didier Werke.

German Glass Industry 51 After September 1945

The blowing end was heated with a small burner on the end of the tank using recuperated air and the burnt gases from this burner were withdrawn down two stacks, one on either side of the blowing end.

The glass was blown in the form of spheres 0.4 mm. thick in sizes varying from 30 cm. to 1 metre (11Ÿ" to 39") in diameter. The curvature of each sphere was tested by template. Very highly skilled blowers were required for this work. Watch and clock glasses were cut direct from the spheres in the Warehouse.

Small Experimental Tank This tank, built on a very small scale and provided with a Fourcault machine 80 cm. (31œ") wide, was an exact replica of the larger Fourcault tank. Ultra violet absorbing glass has been made on this machine during an eight day experiment with fairly promising results.

Glass Composition

Spectacle and Watch Glass SiO2 71.00  
  CaO 11.00  
  Fe2O3 0.04 (approx.)
  Al2O3 0.96  
  Na2O 9.00  
  K2O 7.00  
  BaO 2.00  

4. Furnace Halls

The main furnace hall contained one 8-pot furnace, one 6-pot and two 2-pot, all for casting. The pots were oval, approximately 24" high x 24" wide x 30" long with a wall thickness of 3", and were said to give 200 Kg. per cast. The average life was 20-25 journeys. The pots were handled by an overhead monorail system and cast on a small Chance type machine having six moveable cast iron tables 3 m. long by 1 m. wide. The plates were annealed in a roller lehr, passing first through three positions on a kiln bed. The lehr was 3 metres wide and 54 metres long overall. Stowing was by hand. The rollers were asbestos covered and were gear driven. The annealing principle adopted was to vary the speed, with the glass thickness, maintaining constant temperature distribution, without however, automatic temperature control. The period in the lehr for glass 40 mm. thick was 24 hrs. and for thicknesses up to 10 mm. 4 hrs. The lehr was said to have been working since 1934 and was now being extensively overhauled (kiln bed and rollers.)

German Glass Industry 52 After September 1945

A second furnace hall contained one 6-pot furnace for ladling, a second small Chance type machine and a travelling rail lehr. This lehr also annealed blown cylinders produced in three other furnace halls containing respectively one 8-pot furnace, one 6-pot furnace and one 4-pot furnace, each furnace having several built-on glory holes and also adjacent swing holes. These furnaces had low crowns and they took a larger pot than those used for teeming.

5. Pot Rooms

All the pots were made in the Works, using a Grossalmerode mixture only. This consisted of one-third raw clay, one-third potsherds and one-third burnt clay purchased from the Vereinigte Grossalmerode Tonwerke; no extra silica is added. The wetted mixture is soured for 6 months before using and the pots, hand made, are dried slowly and then stored in hot rooms, not being taken for use until 12 months after making. Debiteuses are also made for the tanks.

The stock of sound pots amounted to 150-200 pots (described as 1 year's stock.) In addition the rooms contained a number of Jena pots brought here for storage; these were circular with two lugs half-way up the outside and were said to have a capacity of 600 litres.

6. Pot Spectacle Glass

A record sheet for a found of “Cast Optical 10 mm. substance” glass made on 3rd April, 1941, gave the following details: Furnace 13, pots 1 and 2, Age of the pots 14. months, Pot mixture Al 2, No. of melts 6.

Batch Mixture: Sand 100 Kg  
Soda   24.5 Kg  
Potash   11 Kg  
Chalk   30 Kg  
Saltpetre   2.5 Kg  
Sulphate   1.6 Kg  
Antimony oxide   800 gm.  
Titanium dioxide   800 gm.  
Selenium (metallic)   4 gm.  

The following temperatures were stated to be recorded by the crown thermocouple:

German Glass Industry 53 After September 1945
Time Temperature Comments
0 hrs. 1,280°C.  
2 hrs. 1,350°C. 1st fill
5 hrs. 1,380°C. 2nd fill
10 hrs 1,440°C. plug
11 hrs. l,450°C. stop
16-20 hrs. 1,100°-1,130°C. casting

Cutting room yield: 356 kg. IIa.

A general casting cycle was given as 28 hrs., with a maximum temperature of l,500°C. and casting temperature of l,100°C. No stirred glass was made in this Works.

7. Protective filter glass (U.V. absorbing glass)

An attempt had been made to make this glass by the Fourcault method, melting first in a pot and then ladling into the drawing pit; the experiments were interrupted when the Works had to close down. A sample of the glass obtained was available for examination; the quality was not good but the experiments were described as promising. Considerable quantities of this glass were made during the war by the blown cylinder process, giving a fire-finished product not requiring grinding, and polishing. Although 12 shades were made, the chief demand was for six principal ones,, All were sent to customers (small optical works) in Fürth and in general all the glass made was despatched irrespective of variation in shade. Typical batches were given as:

Shade 9
Shade 12
Sand 100.00 kg. 130.00 kg.
Soda 38.00 kg. 38.00 kg.
Chalk 18.00 kg. 18.00 kg.
Iron oxide 9.00 kg. 14.00 kg.
Potassium chromate 0.90 kg. 1.40 kg.
Nickel oxide 0.45 kg. 1.40 kg.
Charcoal 0.75 kg. 0.90 kg.

Samples of this blown U.V. absorbing glass were obtained.

8. Clock and Watch Glasses

These were made by blowing spheres from 30 cm. to 1 metre diam., the workmen were described as highly skilled. The substance range was 0.4 mm. to 1.2 mm. The spheres were cut into rough rectangles approximately 25 cm. x 50 cm; these were given a cursory examination for quality and were then circled and sent to Grünenplan for bevelling.

German Glass Industry 54 After September 1945

9. Lens Blanks

This department contained 17 presses with a monthly output exceeding 500,000 lens blanks. The output for an average operator in 8 hrs. was given as 2,000 a good operator reaching 3,000. The blanks were sent to Jena and elsewhere for polishing.

10. Bending Kilns

About 20 bending kilns were installed towards the end of the war for making searchlight mirrors but were never used.

11. Laboratory.

This Works had a small laboratory for carrying out the simpler analyses and for determining refractive indices and relative absorptions.

12. Warehouse

The spectacle glass was examined under edge lighting and normal quality glass contained 0.08 bubble per square decimetre. The glass delivered into the Warehouse gave a circle yield of about 48%.

German Glass Industry 55 After September 1945


  Target No.
Map Ref.
Name of Target Vereinigte Glaswerke, Werk Stolberg
Address Stolberg, Aachen
Date of Visit 8th August, 1945
(also by J.H.W. 23rd September, 1945)
Products Plate Glass (Rough Cast and Polished)
Rolled and figured glasses
Wired glass
Bent glass
Special white glass
Present Position Production was stopped in September, 1944. Buildings (in some cases the plant also) have been extensively damaged having had seven bombs and about seven hundred shells particularly in the Pot Rooms, Casting Hall, Grinding and polishing, Bevelling and Silvering Departments and Warehouse. Pot stocks have been destroyed. An increased power supply is necessary before a tank can be started up. Repairing of buildings and some pot making has been commenced.
Key Personnel Herr Lambert von Reis (General Manager for Germany for St. Gobain Co.)
M. Lamesch (Local General Manager.)
Herr Benden (Secretary)
Dr. Bourggraf (Works Engineer since 1940.)

We were shown round the Works by M. Lamesch and Dr. Bourggraf. Herr von Reis left the area in September, 1944.

Furnaces, Plant, etc. 3 Rolled Plate Tanks
1 Plate Tank
4. 16-pot furnaces
Bicheroux casting plant
Disc Grinding Shed
Pot Rooms
Bending kilns
Employees Pre-war

Special Note The visit to this factory entailed a very long and hazardous journey from the nearest available camp, over very bad

German Glass Industry 56 After September 1945

roads. Since the Hertzogenrath factory was visited first, little time was left to inspect the Stolberg factory. Essential details were noted and tentative arrangements made to re-visit the Works at a later date. During the following days other factories at which similar products were manufactured were visited. It was then decided, owing to lack of time, that the further visit should be made only by one team member (J.H.W.)

Description of Plant, Processes, etc.

1. Gas Supply

The gas was supplied from five Chapman producers, one producer to each tank and one for the pot furnaces.

2. Rolled and Wired Glass Production

There were three small tanks of standard design, constructed of Didier Werke blocks throughout. The gas and air were fed in from the regenerators through two upcasts - one at the hot end, the other at the cold end of the regenerators - and these two upcasts supplied four ports. There were no midfeather arches in the ports so that the gas and air mixed and burned before reaching the port mouths.

Each tank supplied one Boudin type machine and before the war no fewer than eighty-four products were made.

Smooth rollers were used for the production of wired glass. The casting rollers were generally:- Top Electro-cast from Krupps Grusonwerke (the composition is only known by the makers); Bottom cast iron. They required polishing every four days.

The lehrs were of usual design, direct fired and gear driven.

Production performances were almost identical with those of Gelsenkirchen - Schalke.

The lehrs were divided into sections for the purpose of lubrication and automatic oiling was used. The pumps were of similar construction to the oil pump of a motor car and were worked by means of hand operated levers.

Wire All three types: (a) 6 mm. Square mesh - not welded
    (b) 12 mm. Square mesh - spot welded
    (c) Hexagonal

were bought from Deutsche Metallnetz-Werke at Emmerich-a-Rhein;

German Glass Industry 57 After September 1945

and C. Schmidt at Niederlahnstein, in rolls 100 metres (328 ft.) long.

3. Plate Glass Production

This consisted of one Plate tank with all Corhart sides at the melting end and Didier material at the working end. The tank house was very badly damaged and it was stated that it would take 6 to 8 months to get going again.

The tank had a drop arch about 12 ft. wide strutted with steel beams. The sides were Corhart up to about 15 ft. from the rolling machine where they were aluminous clay covered with “sawdust” insulation bricks. The crown was of silica brick about 14" thick, not insulated. These crown bricks were very big, being about 8" x 5" x 14". There were three stacks on each side and the port midfeathers finished in the vertical position so that combustion must start in the port and not in the tank. Two sets of floaters were used and two filling pockets with silica arches on the front of the tank.

Production was stated to be 750,000 sq. ft. per month.

In the lehr the first section of rollers, 40 in all, have cooling water tubes passing right through the centres and delivering the water into a trough running alongside the lehr. They also had hand pump lubrication of roller bearings.

It was proposed to restart the tank before the pot furnaces.

4. Pot Rooms

These were appreciably damaged and there were no pots in stock fit to use, most having suffered through exposure to weather. Clay stocks were considered to be good enough to start pot making and 1 pot had already been made but there were no prospects yet of renewed supplies of French and Belgium clays. Shortage of power was considered to be the biggest bar to getting under way. Grossalmerode clay was used for making pots for the Sindorf factory but not for the Plate pots used here.

Cast pots were made here before the war but the process was discontinued in 1939 and the plant had been appreciably damaged, a bomb having fallen nearby. During the war only hand made pots were produced, the :lays used being of French and Belgian origin. A typical pot mixture was described as 33% raw clay mixture, 25% sherds, 25% grog and 17% ground silica but the proportion of the latter was varied according to the alumina content of the raw clay. A number of mixtures had been made up using broken green pots.

German Glass Industry 58 After September 1945

The method for drying full size Plate glass melting pots in 14 days after completion was described in general terms, the pot mixture being made up from equal parts of French raw clay, French burnt clay and grog (through 16 mesh per sq. cm.) It was aged (“Soured”) for 6 months. The pot bottoms were laid down by hand and rammed with a pneumatic rammer after which the side walls were built up to a wooden former by hand followed by the rammer. The pots were dried in the device described in the following paragraph.

Early in the war two double-track dryers were built for drying hand-made pots. The pots were built up on cars and then pushed into a dryer made up of individual chambers approximately 10 ft. square, the separating walls being moveable wooden partitions. The first chamber had a weighing machine in it for determining the rate of loss of moisture. The chambers contained vertical tubes (14 in. diameter) for passing warm conditioned air down into the pots from which it overflowed and passed out of the chambers through slots in the flooring. The tubes telescoped to permit the pots to be moved. The pots were pushed one chamber forward every second day. Temperature and humidity records were not available but full information was said to be on file in the St. Gobain Company's Paris Office.

A start had also been made with producing tank claywork.

5. Bicheroux Plant and Pot Furnaces

The furnace hall was very badly damaged. There were four furnaces of 16 pots each similar to those at Herzogenrath, but we were told they used 1,000 litre (35.3 cu. ft.) pots.

The pots were brought from the furnaces by a travelling machine bearing tongs, there being one machine on each side of the furnaces. The pots were put down on a travelling car to be picked up by the casting crane.

There were two casting tables and two lehrs with kiln beds and travelling rails. The thickest glass made had been 25 mm. and the thinnest 7 mm.

No additional furnaces were built during the war. The pots left in the furnaces were badly holed but rather good as regards “fangs.” Two mechanical producers of the usual type provided the gas for the furnaces and pot arches.

Nothing was working on the plant but one furnace was ready for warming up.

The glass “horses” were constructed of steel and ran on a full gauge track.

German Glass Industry 59 After September 1945

The white glass made in this Works was decolourised using cerium and praesodymium compounds. No special white glass war products were made at this Works.

6. Bevelling and Silvering Department

Buildings were appreciably damaged but the machines were probably workable. There were several sleek removing, repolishing machines with travelling tables and single polisher heads.

7. Grinding and Polishing Department

The buildings were badly damaged and some plant required replacing. There were five Belgian (H.M.S.) type machines but it was said they had not been worked for the past 10 years. In the Disc Grinding Shed there were 6 grinders and 5 polishers with probably 12 - 15 tables. A washing machine had been completely destroyed. Continuous pumping was having to be done to save the motors in the caves. There were no other grinding and polishing machines in this Works.

8. Bending Plant

One large kiln would give bends with plates 6 metres long by 3 metres wide. Most small bends were done several at a time in this large kiln but there was also a smaller kiln. There was no continuous bending plant.

9. Warehouse

The warehouse had been completely gutted and the general stores partly destroyed. The office block was intact but part of the drawing office was said to have been damaged.

Rough cast stocks were badly shattered and practically worthless.

German Glass Industry 60 After September 1945


  Target No.
Map Ref.
Name of Target Vereinigte Glaswerke, Werk Herzogenrath
Address Herzogenrath, Aachen
Date of Visit 8th August, 1945
Products Plate glass
Toughened Plate glass
Special White Plate glass for Portlights
Fibre glass
Present Position Production was stopped in September, 1944 Buildings (plant to a lesser extent) have been appreciably damaged, particularly the Pot Rooms, Furnace Hall, Bevelling and Toughening Departments and the General Stores. Grinding and polishing could be restarted within eight weeks of receiving adequate power and transport. Supplies of French clay and other raw-materials are required before restarting melting: say, three to four months from date of receiving these before starting production.
Key Personnel Herr Lambert von Reis
(General Manager for Germany for St. Gobain Co.)
M. Lamesch (Local General Manager)
Herr Benden (Secretary.)
Herr G. F. Peltzer (Chief Engineer.)

We were shown round the Works by Herr Peltzer. Herr von Reis left the area in September, 1944.

Furnaces, Plant, etc. Four 16-pot furnaces
Bicheroux casting plant
Disc and continuous Grinding Sheds
Pot Rooms
Twelve Toughening furnaces
Fibre glass furnaces and weaving machines
Employees Pre-war
German Glass Industry 61 After September 1945

Description of plant, Processes, etc.

1. Glass Fibre Department

This was certainly the most highly developed fibre plant seen during the tour. It was the only one to compare favourably with U.S. practice. Electric power was drawn from the Cologne Grid system, but there were two Diesel generators in case of breakdowns, and a transformer for the grid system current.

The Owens-Coming method was used making fibre from marbles (made at Sindorf) in small platinum furnaces with electric heating. There were said to be 20 of these furnaces in two banks of 10 each but only one such bank was seen. Melting rate was, before the shut down, 3œ tons marbles per furnace per month to produce 2œ tons fibre per furnace per month. One woman serviced ten furnaces and two women attended to all the drums on the floor below, power consumption per furnace was 5 Kwh at 1,100°C. and 1 Kilogram of the fibre contained a length of 180 Kilometres.

There were 800 yarn twisting spindles, six Swiss weaving machines each 1 metre wide, but these cannot be started up until the firm obtains permission to bring in the operator from Switzerland. There are also six tape machines for 3 cm. wide tape. A sample was taken. It was claimed that 24" ends could be wound to make packages for wire covering. If successful this is said to be very good.

2. Pot Rooms

These buildings were badly damaged but the machines (2 horizontal mixers and 2 small pugging machines) were in no visible need of repair. The pots were hand made in cores. They are oval and stand on 2 layers of canvas on a strong wire screen of œ" mesh. These cores had a four-track pot drying installation which had several chambers each taking one pot per track. A vertical tube in each position passed conditioned air down into the pot. Pots were said to be dried in three days after which they were stored for a month before use. Enough pots were available to start up one furnace but the stock of clays was very low and the management was anxious to get permission to import Belgian or preferably French clays. They did not consider Grossalmerode a suitable clay for their pots. The latter average 18 founds, hold 800 litres of glass and were about 3œ" thick in the walls. (Thicker than at Grünenplan but much larger pots.)

3. Furnace Hall

Here there were 4 regenerative pot furnaces each containing 16 pots. These worked 3 at a time with one under repair, the life

German Glass Industry 62 After September 1945

between repairs varying between 1 and 2 years. The furnaces were of Dinas Silica except siege and pillar blocks, which were of aluminous clay and were made in the firm's pot rooms. These siege blocks were very large being about 4 ft. by 4 ft. but about one foot thickness. The furnace pots were of the old type, single upcasts for air and gas, the air being behind the gas. The crowns were full centre and did not appear to be insulated. Pot spacing was only about 6" and the siege was fairly level and clean. It was about the usual 4" higher than furnace hall floor level. The melting cycle was 25 hours. The pots remaining in the furnaces had been used for melting a greenish glass; they showed metal level wear and worn holes but were “fanged” hardly at all. Electric filling machines ran on rails the full length of the furnace hall. Warming up furnaces was done by coal fires built behind the tweels (vertically lifting doors) and fired through the tweel filling holes. Each furnace had its own stack. There were 8 double pot arches for coal firing and 3 with gas firing.

4. Gas Producers

There was a battery of eight mechanical producers with automatic revolving bases and de-ashing arrangements, but charging was done by hand through covered bells similar to those at Witten. Three producers supplied gas to two furnaces.

5. Rolling Machine

The Bicheroux machine was of the normal table type. There were three tables each delivering into its own lehr. Stowing tools were the overhead kind. Three plates were cast per pot each 6 mm. substance, 4 m. wide x 8 m. long. This substance when ground and polished was mostly used for motor car windows and screens, but 8 mm. material was cast for shop installations. The lehrs were said to be 50 metres long and had kilns and rails.

6. Rough Cast Stockroom

This could stock 200,000 ft. of plates. It was very badly damaged and less than 10% of stock was salvageable.

7. Grinding and Polishing Department

This had two sections: Disc and Continuous, both being undamaged. In the Disc Grinding shed there were three grinders and three polishers with thirteen tables each nine metres in diameter, the output being given as 300,000 sq. ft. per month. The two Continuous grinding and polishing machines were installed in 1924 and had H.M.S. heads set at an angle across the machine; they were short, being 50 metres long. This section also was said to have an output of 300,000 sq. ft. per month. There were also 6 H.M.S. repolishing machines (18 felts each.)

German Glass Industry 63 After September 1945

8. Bevelling Shop

Badly damaged.

9. Toughening Department

This occupied two buildings. The first building was badly damaged and some plant damaged also. There were eight furnaces below ground level, one being for bent glass. One blowing box was opened; it had large holes about Ÿ in. diameter with about three inches spacing and each hole was surrounded by a ring of fine holes about œ mm. diameter. All the furnaces except that for bent glasses had hinged blowing boxes of this type whilst this had a tubular frame with drilled holes. The second building had a continuous furnace with an output said to be 200,000 sq. ft. per month and also three furnaces of a similar type to those in the previous building. All furnaces seen operated with the glass vertical. The time available was limited; these furnaces require further examination.

This Works had no stock of polished glass.

A direct railway line connected the Works with the associated Stolberg Works.

German Glass Industry 64 After September 1945


  Target No.
Map Ref.
Name of Target Vereinigte Glaswerke
Zweigniederlassung der Aktiengesellschaft der Spiegelmanufakturen und chemischen Fabriken von. St. Gobain, Chauny & Cirey
Address Mannheim - Waldhof
Date of Visit 21st August, 1945
Products Rough rolled plate, cathedral and wired glass.
Present Position The Works has been severely damaged by air raids so that the rough melting process only could be worked. One furnace with auxiliary plant was in operation and the larger one was under repair. The latter could be put into operation within 3 months if the necessary coal was made available. No polished plate has been made since 1930.
Key Personnel Herr Krafft (Manager)

Herr Jungfleisch (Asst. Manager)

Herr Bruggemann (Sales Manager)

Plant Consists of:-
1 Furnace 8 x 4 x 1.5 m. (Out of action)
1 Furnace 6 x 3 x 1.5 m. (running)
4 Old type Morgan static hand fed and poked producers, 2.7 m. diameter
2 Plain and Cathedral rolling m/cs.
1 Machine for wired glass
2 Annealing lehrs
1 Waste heat recovery plant (not in operation)

Above in working order.

Remainder of plant viz., grinding and polishing shops, bending shop and Electrocast refractory block plant had been completely wrecked by air raids.


Employees Pre-war
German Glass Industry 65 After September 1945

Description of Plants processes, etc.

1. General

The plant, associated with the St. Gobain group, was the first to be installed in Germany for the manufacture of rolled flat glass by the Boudin process.

It comprises two comparatively small tank furnaces measuring 6 x 3 and 8 x 4 metres respectively; each furnace supplies glass to one rolling machine. The furnaces are of the end fired regenerative type, and are heated with raw producer gas made from hard coal in Morgan static type gas producers. The smaller furnace was in operation and was melting 20 tons of glass per day which was being rolled into figured window glass 3.5 mm. thickness. Rate of production was 2.4 - 2.5 metres per minute of sheet 1.2 metres broad. This was cut with steel wheels in a manner identical with that at Gerresheim.

2. Furnaces

The furnaces were of simple sprung arch construction, end port fired and lined with Didier tank blocks. The single port at each end was long and narrow - about half the width of the furnace. It did not contain any passages for deflecting the gas and air into the melting chamber of the tank furnace. The glass was withdrawn from the side of the tank quite near the port, and it flowed along a short channel to the machine. It was stated that reversal of the furnace did not affect the condition of the glass flowing to the machine. The melting temperature was 1,500°C. and the temperature of the glass at the machine was about l,000°C. The life of the tank was 15 months but hot repairs to the upper course of blocks were carried out every 3 months. The excessive wear was caused by the use of a high proportion of sodium sulphate in the batch because of shortage of alkali. The depth of glass was 1.5 metres and the capacity of the smaller furnace was 60 tons of glass.

3. Batch Composition

Sand 264 kg
Soda 78 kg
Lime 98 kg
Sodium Sulphate 6 kg
Selenium 0.002 kg

The sand is from the Pfalz district near at hand and is used wet in the received state. There is nothing of note in the batch handling plant. The furnace is charged through a wide doghouse by means of a large mechanical flat scoop, at least 3 feet in width. A very considerable quantity of cullet and batch were charged at one filling.

German Glass Industry 66 After September 1945

4. Glass Making

A water cooled clay skimmer block was used in the out­flowing canal. The glass then floeed through the Boudin machine and was carried through a comparatively short lehr on rollers. The in-going rollers were water cooled, while the last rollers were covered with wooden reels. The bottom roller of the Boudin machine was figured and the top roller was plain; each roller was about 4-5 inches in diameter. The sheet of glass coming from the lehr was cut automatically into two sheets by means of steel cutting wheels. It was cut transversely into suitable lengths by hand and packed into wooden crates using a small amount of straw packing.

Miscellaneous The gas is made in an early stationary type of Morgan producer of 2.7 metres diameter. Each producer gasifies 7-8 tons of coal per day. Each furnace is operated from its own producer and steam is raised by means of a waste heat boiler utilising the outgoing gases from the melting furnaces in the case of the larger furnace.

The Works also contained plant for making electro-fused Corhart blocks which had been destroyed by bombing. This plant had never been operated but it was intended to do so before it was destroyed and an engineer had been sent from Modane to start production of these blocks for Germany. Corhart blocks from Modane were used for the upper course in the tank furnaces at Waldhof but were unobtainable during the war.