Washington Densometer

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Washington Densometer


Soil Science


Physical Description

Main apparatus:  The Washington densometer is comprised of 16 pieces (The kit owned by MTU does not include all 16 pieces). The first of these pieces are 4 aluminum calibrated rods, which have a large hexagonal head on them, screw threads at the base, and an inscription reading from 4 to 16 at each inch mark. Then there are two four-inch long aluminum bleeder plugs with an inscription from 0-4 at each inch mark and screw threads at the top and bottom. There is then the aluminum cylinder cap that has a hole in the exact middle which the bleeder plugs are able to penetrate, along with a small pressure release valve. A piston comprised of aluminum and rubber gaskets sits underneath the cylinder cap and is fitted with screw threads at the top to join to an adapter. The piston sits in the main body of the apparatus. The main body of the apparatus is a hollow aluminum cylinder that sits upon a main valve made of brass, complete with a blue painted knob. This main valve is then attached to an aluminum cast coupler. This coupler allows the main valve to attach to a conical cast aluminum base with a fitting at the top that fits the coupler, also called the Head. On either side of this base, two “wings” are present that allows the conical portion to be attached to another base.

Two ground bases are available for the apparatus. One is called the carrying base which is a green painted wood and aluminum base that is a square, flat, piece of wood upon which a short hollow cylinder is placed. On either side of the cylinder are two brass screws with two wing nuts that fit into the wings on the Head and allows the bases to join. The second possible base is a circular piece of wood with a circle cutout in the center, also called the Template. The circular cutout has an aluminum fitting around the edge in which one of three different height hollow columns can be placed. Two brass screws with wings nuts are also present on the wooden base so that the conical base can be attached. Three aluminum rings are also present, whose exact volume is known. These rings are used for calibration of the tool. A flexible suction tube is also part of the kit. This tube is made of a spring that resides inside of a silt screen. A tapered aluminum sleeve, with interior screw threading is also present.  The kit also includes 2 quarts of D-87 soluble oil, and 1 pint of D-87 soluble oil. An extra rubber gasket was also included in the kit, though the reason for it is unknown.

According to photos found in the “Suggested Method of Test For Density of Soil in Place Using the Washington Densometer”, it looks like the kit that is housed at Michigan Technological University is missing parts. Parts that are not included in the kit are a recharging valve, a balloon, and a locking ring.

The apparatus is housed within a large wooden box with steel handles on the sides for transportation.

Functional Description

To use the apparatus, the user would first assemble the apparatus with the template base. The Densometer would then need to be calibrated appropriately. In the use of the Densometer an initial reading, a final reading, and a ring constant would be recorded. With these reading a volume would be produced. The soil removed from the test hole would be measured for weight. With these two measurements, the density of the soil can be determined.


1960s or 1970s




physical object


USDA property tag 061040-00900



Physical Dimensions

Total Height: 91 cm
Transportation Base: 30 cm x 30 cm
Template Diameter: 60 cm
Calibration Rings Diameter: 23.5 cm
Cylinder Diameter: 10.5 cm
Calibration Rods: 55 cm
Storage Box: 65cm x 115cm x 39 cm


Aluminum, brass, wood, rubber, fabric


Charles R. Watts Co., Olympia, WA


“Property of Dept. Agricultural Forest Service”
“Property of USDA Forest Service”
“Washington Densometer Patent no. 493183”
“D.G. Parrott & son”
“Olympia WA.”
Piston inscription “1353”

History of the Object

The Washington Densometer was fabricated in Olympia, Washington by D.G. Parrott & Son. This particular Washington Densometer was originally owned by the U.S. Forest Service in Houghton, Michigan and was donated to Michigan Technological University. The year of donation is unknown. This instrument is within the field of soil sciences, which is now a part of MTU’s School of Forestry and Environmental Sciences. Forestry was added to Tech in the early 1900’s (1925-1935) under the school’s president at the time William Hotchkiss.


Dillman Building, Room B010A Sub-basement


ASTM Committee D-18, STP479-EB “Density of Soil in Place Using Washington Densometer.” In Special Procedures for Testing Soil and Rock for Engineering Purposes, 5th ed. (West Conshohocken, PA: ASTM International, 1970). doi: https://services.lib.mtu.edu:5021/10.1520/STP479-EB

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“Washington Densometer,” Michigan Tech Inventory of Historic Scientific Instruments, accessed April 13, 2021, https://ihsi.omeka.net/items/show/197.