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Viscosity Measurement

The Bostwick Consistometer is invaluable to many industries to standardize production lots. It is a simple, dependable instrument, which accurately determines sample consistency by measuring the distance which a material flows under its own weight. The unit is manufactured from stainless steel and has two leveling screws and a level. The reservoir accepts a 75ml sample. A spring-operated gate is held by a positive release mechanism, permitting instantaneous flow of sample to be measured. The trough is graduated in 0.5cm divisions to permit accurate measurement of flow. Complies to R-81294D and ASTM F1080-93. Portable and easily cleaned, the Bostwick is 14 inches long x 3.5 inches wide x 5 inches high and weighs under 2kgs.

Procedure

The compartment that has a guillotine-type system is filled with a given volume. At t=0, the product is released and the consistency parameter obtained corresponds to the distance covered by the product front after 15 seconds of flow. The only control condition of the measurement is the product temperature:  (NOTE: See product Specification for identified Bostwick readings).

Sample Measurement:

The consistency of the finished food is such that its flow is not more than 14 centimeters in 15 seconds at a desired temperature when tested in a Bostwick Consistometer in the following manner:  
(The trough must also be at a temperature close to 20oC)

Step 1- The Bostwick Consistometer is designed to sit at a specified angle. The instrument must be adjusted to ensure that it is at this angle. Locate the two twist screws in the rear of the instrument as illustrated in I. Both of these may be adjusted to raise or lower the sides of the instrument. Adjust the two screws until the leveling bubble on the front of the instrument is centered as shown in II A and II B.

 

Adjust end-to-end level of Bostwick Consistometer by means of the spirit level placed in trough of instrument. Side-to-side level may be adjusted by means of the built-in spirit level.                    Bostwick Consistometer: must be adjusted to ensure that it is operating at the correct angle of incline.

 

Step 2- Close the product gate by pulling it down (A) and while holding it in this depressed position, pulling the lever arm up as far as it will go (B).     The product gate is now in its cocked position (C).

Transfer sample to the dry sample chamber of the Bostwick Consistometer. Fill the chamber slightly more than level full, avoiding air bubbles as far as possible. Pass a straight edge across top of chamber starting from the gate end to remove excess product. 

Step 3- Pour the desired sample into the sample reservoir as shown in A and B. Fill the reservoir up to the top of the product gate (C).



Release gate of instrument by gradual pressure on lever, holding the instrument down at the same time to prevent its movement as the gate is released.

Step 4- Release the product by pressing down on the lever arm (A). Allow the product to run along the slope for 15 sec (B).   Immediately start the stop watch or interval timer, and after 15 seconds read the maximum distance of flow to the nearest 0.1 centimeter.

 

Step 5- Look at how far the product ran down the slope in the 30 sec. The slope has graduation marks indicating the distance in centimeters. Record this value as the consistency of the product.

 

Clean and dry the instrument and repeat the reading on another portion of sample. Do not wash instrument with hot water if it is to be used immediately for the next determination, If readings vary more than 0.2 centimeter, repeat a third time or until satisfactory agreement is obtained. Report the average of two or more readings, excluding any that appear to be abnormal.

Step 6- Clean the Bostwick Consistometer with warm soapy water. Completely dry the instrument before using it again.  It is very important that the Bostwick Consistometer be dry before using it. Water will decrease the friction coefficient of the instrument and result in false readings. 

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