Theatre Design & Technology - Summer 1978 - 42

Fig. 4

PROPANE TANK
WITH VALVE 8REGULATOR

GAS BURNER
OPERATIONAL SET-UP

with a 7 inch (18cm) radius and a 14 inch (49.5cm) feeder stud. A
special bracket was constructed both for mounting the unit inside the
monolith and for supporting the orifice in proper alignment with the
gas-air mixing chamber. By making a slightly oversized and elongated hole in the bracket, the orifice could be adjusted to mate
properly with the mixing chamber. During construction, all brazed
joints were tested for leaks with compressed air and soap-water
solution. At final assembly, threaded joints were taped with teflon
sealing tape. Those joints, as well as the compression fittings, were
again tested with soap solution.
During a test burn, it was discovered that the burner was too
efficient. It burned with a hot, blue flame just like the oven burner. The
air dampers on the mixing chamber had to be adjusted for a slightly
richer mixture to provide a larger, but cooler, and more attractive
orange-yellow flame. After several test burns of some length each, it
was determined that, because the flame was actually slightly above
the gas jets, the E.M.T. remained quite cool and no deterioration of
the jets was observed. The metal near the jets was only slightly more
than uncomfortably warm to the touch immediately after extinguishing the flame, and the feeder stub was completely cool to the touch.
In order to mount the burner in the snow saucer (Fig. 3), it was
necessary to cut a slot rather than a round hole in the saucer to
accommodate the radius bend of the feeder stub and allow the
burner to sit close to the bottom of the saucer. Because it was desired
to control the liquid (water) which was to be poured into the saucer,
the slot was dutch-manned with window screening and hydraulic
cement and a small drainage hole was drilled and fitted with a hollow
brass rivet over which small diameter plastic tubing could be pushed.
The liquid could then be poured into the edge of the saucer and it
would drain through the tubing into a container under the monolith. In
this way, the liquid could be kept out of all the working parts and off
the floor.
A trip to a local fireplace and patio shop yielded lump pumice and
"Flower Rock" (sold for use in gas barbeque grills). When arranged
around the burner, these materials provided a very convincing and
non-combustible bed of coals. An added advantage of the bed of
coals was that the coals partially blocked some of the jets and thus
broke up the burning gas patterns, softening the sharp geometric line
of the circular flame, making it much more natural looking.
The final set-up of the burner unit is shown in Figure 4. A hole was
drilled in the stage floor beneath the monolith and % inch (9mm)
copper tubing was run through the trap room to the operator's position where another hole was drilled and the tubing run back up to
stage level and connected as shown in the figure. A handle extension
was added to the operator's control valve to make movement and
fine adjustment of the gas supply easier.
After several ignition systems were considered and rejected, a
sparkgap arrangement was constructed. Two points were cut from a
remnant of tungsten rod that had been used in the T.I.G. welding setup. These points were aligned in electric wire lugs fastened to a small

piece of asbestos board (Fig. 5). The assembly was then attached to
the burner with a conduit strap in such a way as to place the gap
between the points very close to one of the jets and directly in the gas
stream (Fig. 3 and 5). A neon sign transformer was used to power the
points. With this arrangement, the switch is closed before the gas
valve is opened and a continuous spark will jump the gap until the
switch is opened again. Thus; the spark is always available at the
moment when the fuel-air mixture in the chafer reaches the critical
level for ignition. This method was 100% dependable and ignition
always resulted in a smooth swelling of the flames. The gap setting
was non-critical; it could be anything up to V. inch (6mm) and still
work.
o

ROCK
WALL

Fig. 5

/ W 1 R E CLAMPS

crJ--- -----.CJs
~I T ( )
I

POINT

ASSEMBLY

5,OOOv.
30mo.
TRANSFORMER

ELECTRONIC
GAS IGNITOR

/I0voc

The transformer was installed in the monolith as close to the chafer
as possible to keep down the length of the high voltage leads. The
secondary of the transformer was wired to the points with high voltage test-lead wire covered with asbestos sheating to protect it from
the flames. The wire passed through oversized holes in the saucer
which were caulked in with hydraulic cement. The primary wiring was
regular stage cable. The points were oriented in the chafer so that
they were on exactly the opposite side from where the liquid would be
poured. To further protect the actor who was to pour the libation (in
the event of operator error) the actor was instructed never to touch
the chafer, and his pitcher was constructed of non-conductive material.
Dramatically, the fire was quite successful. As the flames began to
rise gently from the chafer, they combined with the setting, lights,
costumes, and action of the play to produce a beautiful and moving
moment. No artificial fire could have provided the same character
and movement as the dancing flames. All in all, everyone was
pleased with the way the flame performed.
From a safety viewpoint, risks were reduced to the point where
those connected with the production thought they were acceptable;
but it cannot be emphasized too strongly that this article is not to be
construed as a recipe for the construction of a fire to be used on
stage, but rather as a retelling of the process that one theatre used to
provide an effect under a given set of circumstances. The University
Theatre was fortunate that the circumstances of this production were
such that they readily allowed the use of this particular unit onstage.D

Roger B. Burch is Technical Director for the Krannert Center for the Performing Arts at the University of Illinois, Urbana-Champaign.
John Scharres is Technical Director at the Woodstock Opera House, Woodstock, Illinois.

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