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15 Oct 2011 - More temperature records

The goal of this day was to get some additional temperature measurements for different designs of furnaces for a paper we are working on.

The outcome of this series was the paper:
Glass on Fire: Temperatures in reconstructed Viking Era bead furnaces, in "Can These Bones Come to Life?" Insights from Reconstruction, Reenactment, and Re-creation Vol II. It is available from Freelance Academic Press.

We ran three furnaces this time - the "Sarah", the "Goderich", and the "Neil".

Furnace NameArchaeologyDescriptionNotes
NeilRibe Circular designA "teapot" design. Single chimney, with annealing pot attached to one side. A single working port cut into the body. Charcoal is loaded through the working port or chimney. Walls are standard thickness (3cm) and have a very pronounced curve joining walls and floor in a bowl shape to aid in charcoal concentration. The working port is cut high on the wall. 
SarahRibe OvalA smaller version of the standard shape built with a single chimney. This had originally been intended to work as a single working port but the plan was changed. A port was cut into each end, and a diverter added to the inside. The air port was cut in the usual location. 
GoderichRibe OvalDual chimney oval furnace, cobb construction. Internal construction includes gentle slopes from walls to floor, and a large air diverter opposite the air port. There is no opening cut for charging - charcoal is added through the chimneys. Working ports are cut into each end. Right port uses cuts angled up into the furnace. Left port cuts angle down into the furnace. Right port produces more heat onto the bead maker.Good functional furnace with 10 hours of burn time.

Several videos were made to allow us to plot temperature over time, both in the chimney and in the door. These are the results.

Operating temperatures

All temperatures are in celcius.

Compressed video (8x normal speed) to go with the chart below

Compressed video (8x normal speed) to go with the chart below

We also got a chance to run and record the "goderich" furnace the next weekend
Compressed video (8x normal speed) to go with the chart below


We also have a few videos available:
Decorating a bead with reticella
Drawing reticella rod
Creating millifiore

The "Neil" furnaceWinding on glassWorking a bead in the chimneyWorking a bead in the chimney
Temperature of "Neil" furnaceThe "Sarah" furnaceWorking in the doorReticella
Pulling reticellaAdding more glassRolling a beadTouchng up an edge
Adding reticellaSarah getting ready

Beads Produced

Black - impacted by atmosphereBlue decoratedBlue with reticellaWasp bead
Wasp bead 2Wasp bead 3Rayed eye beadDotted
Light blueClearBlack with ringed eyeSecond view of bead
Yellow with dotsBead with reticellaSecond viewBlack with red and yellow bands
Second viewWhiteTwo temps


Following this session the bead furnaces were broken down in order to record more information about their construction.


Exterior diameter of base22.5 cm
Thickness of base18 mm
Interior bowl width13 cm
Depth of bowl (to bottom of door)11 cm
Bottom of tuyure to bottom of bowl5 cm
Bottom of bowl to top of chimney22.5 cm

MeasurementTotal (mm)Sintered (mm)Dark Clay (mm)
Wall at base of bowl70.584.5516
Wall half way to door34.914.335.5
Wall at door31.337.2413.18
Wall at top of door25.018.729.08
Wall at top of chimney13.296.275.4
The floor had only a thin amount of sintered clay, most of it was just blackened. At the center of the bowl the black was the full thickness while at the edges there was unblackened clay at the bottom.
On the inside of the bowl the bottom is partially blackened and partially unblackened. The black area is on the side of the bowl closest to the door and covers a part of the interior wall.

Top viewSide viewAir inletOpened between door and tuyure
Wall above doorSide view of cross-section


Exterior length40 cm
Interior length32 cm
Exterior width21 cm
Interior width14 cm
Interior tuyure to diverter8.5 cm
Exterior height25 cm
Interior height (to bottom of chimney)20 cm
Thickness of base18 mm
Interior bowl width13 cm
Depth of bowl (to bottom of door)11 cm
Bottom of tuyure to bottom of bowl5 cm
Bottom of bowl to top of chimney22.5 cm

MeasurementTotal (mm)Sintered (mm)Dark Clay (mm)
Chimney 2nd location167.77.4
Chimney 3rd location16.26.25.2
Top shoulder at chimney22.59.28.2
Top shoulder at chimney 2nd location24.811.911.9
Above Tuyure36.517.712.8
Above Door32.519.311.1
Wall under tuyure351319
Wall under tuyure at base504.538.7

Back viewEnd viewWall below tuyureSide view, wall below tuyure
End view with doorBaseFloor


Exterior width of base25 cm
Exterior length of base54 cm
Thickness of base18 mm
Interior bowl width13 cm
Base to bottom of door2.6 cm
Door height6.2 cm
Base to top of chimney28 cm

MeasurementTotal (mm)Sintered (mm)Dark Clay (mm)
Tuyure wall at base54.5012.52
Tuyure wall 1" up37.187.2910
Tuyure wall 2" up34.9711.4814.38
Tuyure wall 3" up34.6815.913.17
Tuyure wall 4" up30.2913.0514.25
Tuyure wall 5" up31.7511.2510.88
Tuyure wall 6" up23.597.958.69
Tuyure wall 7" up19.2311.517.2
Tuyure wall 8" up21.8510.340
Tuyure wall 9" up20.328.580
Tuyure wall 10" up15.76.910
Tuyure wall at top of chimney15.85.440
Back wall at base40.688.2422.61
Back wall 1" up32.8611.9114.44
Back wall 2" up35.2710.3419
Back wall 3" up32.9514.279.73
Back wall 4" up29.5513.118.25
Back wall 5" up24.0511.065.09
Back wall 6" up21.8312.626.01
Back wall 7" up16.958.624.13
Back wall 8" up17.756.685.66
Back wall 9" up20.728.125.79
Back wall 10" up19.249.116.32
Side wall above door28.7315.519.67
Base a door52.7818.9125.07
Base 7cm in from door255.82All

The inside of the base showed almost no blackening. Just a small amount at the midpoint between the door and tuyure.
Underneath the base (exterior) heat blackening was visible in a fairly regular oval starting about 3cm from the edge. There was no visible difference in the heat marking where the air diverter is found.

End viewBack viewTop viewAir diverter
Door to back wallInteriorUnderside of baseBase cross-section
Plan drawings

Text © Neil Peterson, 2011
Photographs © Individual artists
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