Casting Impression Evidence
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Topics - Casting Impression Evidence
When to cast rather than photograph
Reclosable Zip-loc Bag Method
Pouring a Cast
Casting Suggestions
Cleaning a Cast
Articles - Casting Impression Evidence
When to cast rather than photograph
It is advised to recover impressions by casting when the impressions are over 1/4 inch deep
into the soil. Deep impressions will create interfeering shadows at their low points when
illuminated with an oblique light source. Another time to cast is when impressions having
different orientations are closely aligned to each other. Under these circumstances,
illuminating one impression properly will likely result in a poor illumination of the
adjacent impression having a different orientation.
Reclosable Zip-loc Bag Method
- Purchase zip-loc plastic bags measuring approximately 10 1/2 x 11 inches
( 26.8 cm x 27.9 cm ),that can store 2 pounds of casting material.
- A gallon-sized (3.79 liter) bag has the size & volume for this purpose.
- Weigh out 2 pounds of casting material, and add the material to the bag. Leave
one corner of the bag unzipped.
- Lay the bag on one side, and flatten to remove the excess air. Completely
seal the bag.
Pouring a cast from a reclosable Zip-loc bag
- Using a 12 ounce beverage can as a measuring device, add about 3/4 of a "can -full"
of water to the casting material in the plastic bag.
- Squeeze and massage the bag to combine the water / casting material mix.
- If the mixture is too thick, add the remaining water in the can to the bag.
- The proper viscosity of the mixture should be that of pancake batter. When
this viscosity is achieved, then unzip the bag, and pour the mixture.
- While pouring, the bag should be held at a height of just a few inches above
the impression.
- Casting material is poured on the ground surface just off to the side of the impression,
across from the arch area. Continue to add material until the mixture overflows the
impression, and unto the ground surface. Never pour the material directly unto any
design-bearing or pattern-bearing part of the impression.
Casting Suggestions
*
Lightweight debris which has fallen into the impression obviously after the impression
was made may be removed using tweezers prior to pouring the casting material. DO NOT
REMOVE ANY EXTRANEOUS MATTER WHICH IS PART OF THE IMPRESSION ITSELF.
*
Hair spray may be applied to loose sandy soil as a means to 'bind' the loose particles
together in order to assist the casting process.
*
As the casting material begins to harden, write upon the back (non-impression bearing) surface
of the cast your pertinent case data such as:
- Your initials
- Case Number
- Date
- Impression Number
- Orientation Marks
*
When the air temperature is above 61 degrees F (16 degrees C) allow the cast to set
undisturbed for at least twenty minutes. If the temperature is colder, allow the cast
to harden for a longer period of time.
*
Casts may be removed using your fingers evenly spaced along the cast's length and inserted
into the soil underneath the cast. A 'thin' object such as a spatula used to lift an
incompletely dried or partially hardened cast may result in that cast breaking near the
location at which the thin object had been inserted into the soil.
*
Allow the cast to air dry at room temperature for at least 24 hours before packaging or attempting
to clean any soil or debris adhering to the cast.
*
Air-dried casts may be packaged in sturdy cardboard boxes. Brown paper bags may not be sturdy
enough to 'shield' casts from being inadvertently dropped onto tabletops, etc. Never package
casts in airtight containers or plastic bags which don't allow the cast to air-dry.
Cleaning a Cast
A container with a saturated solution of Potassium sulfate in water can be
used to clean the cast of soil residue.
The cast should be fully submerged in the solution at room temperature. Upon submerging the
cast, streams of bubbles will rise from the cast. After one hour, the cast can be cleaned by
lightly brushing, and/or, thoroughly rinsing with running water.
Footwear Textbooks Containing Casting Instructions
Casting Literature Published in Professional Journals:
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