CART

Silver Nitrate solution

Ready for use Set

Silver nitrate is a very old technique that pre-dates the use of ninhydrin. In the past it was often used on paper but also on wood (untreated), cardboard, and cow horns. On paper it is nowadays only used when physical developer cannot be used (due to the nature or size of the object). Physical Developer (PD) is in general more sensitive so preferred over silver nitrate.
Silver nitrate can be used after ninhydrin but there is no place for it in a sequence with PD.
 
Untreated wood and cardboard boxes are items where the use of silver nitrate solution can be useful.
 
Product #
Description
Quantity
Add
 
 
B-82000
Silver nitrate solution, ca. 27 g/l in ethanol/water (10:1 vol/vol), 100 ml
 
B-82025
Silver nitrate solution, ca. 27 g/l in ethanol/water (10:1 vol/vol), 250 ml
 
B-82050
Silver nitrate solution, ca. 27 g/l in ethanol/water (10:1 vol/vol), 500 ml
 

 

Silver nitrate solution (ethanol/water mixture) can be applied by dipping or brushing (painting). A regular paint brush (kept solely for this purpose and cleaned with distilled water after use) or cotton balls with forceps can be used for the brushing. Due to the oxidising nature of silver nitrate it is not advised to spray the solution. Inhaling the spray can damage the longs. Silver nitrate (solution) colors the skin dark so good gloves and wearing a laboratory coat to avoid contact with the skin and clothing are needed. Contact with the eyes should be avoided at all costs!
 
After the treated item is completely dry (this is important) the process needs some UV-light to develop the prints. The reaction is assumed to be silver nitrate reacting with the sodium chloride in a fingerprint to silver chloride which under the influence of light oxidizes to silver. This process is similar to what happens in photography with film.
Prints come up brown or even darker but over time the whole surface may become grey due to the residual silver nitrate on the surface. For paper that has been dipped in silver nitrate solution it should next be washed in distilled water and then completely dried before exposing to strong light.
 
This silver nitrate solution can also be used on styrofoam (Expanded Polystyrene - EPS).
 
If the surface to be treated has been exposed to high humidity or has been in contact with water silver nitrate may not be effective. The CAST manual states that "Silver Nitrate is not effective on items or surfaces that have been exposed to high humidity or have been wetted, even if they have been subsequently dried." However, the older literature (Scott's Fingerprint Mechanics, Olsen, Robert D., 1978) states that "Silver nitrate may also provide results when examining papers that have been exposed to excess moisture, whereas ninydrin, in such cases, will not. Even after papers have been thoroughly soaked, it is sometimes possible to dry the papers and develop good latents with silver nitrate."