Transcript Physics 11 - NYCC SP-01

Chapter 11
The
X-ray
Darkroom
General Darkroom Layout
If
you are hand developing there
should be a film handling area and
a processing area to minimize the
possibility of solutions
contaminating the film and the
intensifying screens.
If space is limited extreme caution
should be taken.
General Darkroom Layout
When
using an automatic
processor a much smaller room
can be used.
Today many x-ray rooms are
set up so that the automatic
processor is positioned in the xray room.
Lightproofing the Darkroom
Obviously
the darkroom must be
lightproof.
This is best tested by the use of
dental film, half-covered, placed in
various parts of the room for a
period of time, three to five times
the normal film handling time, and
then developed.
Lightproofing the Darkroom
 Any
fog in the portion that was not
covered indicates light leaks. The use of
half-covered film eliminates film fogging
from other sources.
 A baffle entrance is more lightproof than a
door (and permits better ventilation).
 If you have your automatic processor in
the x-ray room, this room, of course, will
have to be light proof.
X-ray Proofing the Darkroom
 The
darkroom must be x-ray proof or
radiation entering can fog the film
being processed or, even more
important, the larger amount of film
being stored in the room.
 This is more important when using
non-screen film, however, screen film is
also sensitive to x-ray.
X-ray Proofing the Darkroom
A
leaded film bin will be needed if you
are processing in the x-ray room.
 The position of the x-ray unit is
important (the primary beam should be
focused away from the darkroom).
 Additionally, the darkroom walls
should be lead lined (see state
specifications for specifics).
X-ray Proofing the Darkroom
The
amount of lead needed is
determined by room size,
material of walls, types of xrays, film/screens used, tube
placement, placement of x-ray
room within the building, and
the x-ray machines capability.
X-ray Proofing the Darkroom
The
adequacy of such protection
can be checked by leaving a loaded
cassette with a few coins or keys on
top in the darkroom for a
considerable number of exposures.
Any exposure occurring can be
attributed to x-ray leakage.
Darkroom Color
 The
color of the darkroom need not be a
black or dull, dark color.
 If the safelight is "safe" all the reflected
light will be too.
 Colors suggested are light green for use
with a green safelight or beige for use
with a red or yellow safelight.
Darkroom Cleanliness
 The
darkroom and all the equipment
and accessories should be kept spotless.
 Dust can cause artifacts on the film.
 Chemical dust from spills can stain film
and screens.
 The solutions should be covered when
not in use.
Darkroom Cleanliness
A
contaminant or scratch on the
cassette will also leave a reproducible
artifact on the film until it is cleaned or
replaced.
 When changing solutions the tanks
should be cleansed with Clorox before
refilling.
 Scouring powder should never be used
as it leaves a gritty dust behind.
Darkroom Temperature
If
you are hand developing, the
darkroom temperature should be
maintained as close to 68 degrees as
is possible as should the developer.
In addition to influencing the
temperature of the developer and
fixer, excess heat can fog the film
stored.
Darkroom Temperature
The
film bin should be as far
away from the heat source in
the room.
Some means of controlling the
temperature of the solutions
should also be available.
Safelight Illumination
 Wratten
6B (yellow) or Series 2 (red)
can be used with a ten watt bulb and
should not be directed at the film being
handled.
 The film should be at least 4 feet from
the safelight at all times.
 The length of time of exposure to the
safelight is also a factor.
Safelight Illumination
Loading
a cassette or putting a
film onto a developing hanger
should take a matter of seconds.
To test just how "safe" your
safelight is, first make a
radiograph in the usual
manner.
Safelight Illumination
 Then
unload the cassette in the
darkroom and cover half of it with
black paper and expose the uncovered
portion of the film to the safelight for a
period usually used in film handling.
 Develop the film for the normal length
of time and examine it for any fogging
in the uncovered portion.
Safelight Illumination
 This
is the same procedure in x-ray
proofing.
 The covering of half the film eliminates
mistaking fogging from any other
source for safelight fogging.
 We should used exposed film because
film exposed to x-rays and light from
the intensifying screens is more
sensitive than unexposed film.
Darkroom Ventilation
Noxious
fumes may present
with use of today's auto
processors. Therefore,
ventilation near the processor is
needed.
Make sure that the ventilation
system is lightproof.
Darkroom Set-up
When
setting up a darkroom,
preplan.
Installation of drains, a sink,
and proper power sources
should be considered initially
as it is costly to add these
necessities at a later date.
Darkroom Tidbits
 For
proper quality control (QC) you’ll
need a sensitometer (controls the
amount of each exposure & makes the
same exposure in each given shot) & a
densitometer (checks contrast, speed &
fog).
 You need to keep track of re-shoots &
log why.