By BOB PADULA
ASI Wool Quality Consultant

(February 1, 2008)  As wool prices reach record highs, the wool trade is becoming increasingly concerned with the amount of contamination in wool.  While a contamination free wool clip is desired, it is not a reality because sheep themselves have naturally occurring contamination such as urine stained wool and possibly other objectionable fibers. Other contamination found in wool is considered either applied or acquired from the environment.   

Understandably, applied contamination garners much attention. Those not familiar with sheep-husbandry practices may not understand why a grower would apply something to their wool, such as an identification mark, knowing it is considered a contaminant and reduces the value of the wool clip. However, as the industry explains the need for easy visual identification along with the use of products specifically made for the sheep and wool industry, the issue seems to fade away – or does it? 

Branding fluid and other sheep marking products are under more scrutiny these days.  In addition to the discoloration of the wool, if the paint brands do not scour out, the brand can become entangled in the processing equipment decreasing efficiency and increasing the cost of processing the wool. Because many products are labeled as ‘scourable’ are promoted to the sheep industry, the sheep producer is lead to believe he or she can use these products with confidence and any potential contamination will not be a problem for the processor. 

In Australia, all branding fluid is manufactured by a single company under the Si-ro-mark license agreement, even though it may be sold under many different trade names. This branding fluid was designed to be scourable and acceptable for use by the sheep industry. However, a study released in 2007 by the Australian Wool Exchange reported 142 lots known to contain paint brand contamination, 41 percent failed the test for scourability after scouring and carding. As expected, lots subjectively identified by AWEX-ID (Australian Wool Exchange Identification) as containing medium (R2) to heavy (R3) paint-brand contamination had greater failure rates compared to those lots containing light amounts (R1) of paint brands.

The report went on to indicate that even though Si-ro-mark branding fluid is specifically made and considered scourable, it may not totally scour out to the satisfaction of the mill if the fluid was not used according to label recommendations and specifications. 
 
In the United States, paint branding is not only a helpful husbandry practice, it is a legal requirement in some areas. Therefore, paint branding can not practically be eliminated from the U.S. wool clip and growers using paint brands should take steps to minimize the problems and concerns for processors. Heavy, hard-crusted brands do not easily scour out and should be avoided. In addition, thinning of branding fluid by adding solvents or excessive heating can cause the chemical composition to be altered making the brands unscourable. Branding should take place as soon after shearing as possible to allow brands to fade and break up due to exposure to the environment prior to the next shearing.
  
In addition to branding fluid, other identification marks are of concern for processors. There are many different forms and types of identification methods available for growers from chalk and marking sticks to aerosol cans of marking fluid. Some of these marking sticks, aerosols and other forms have been tested and are reported to be scourable, however, many are not. 

It is recommended that all identification marks be treated as ‘non-scourable’ and marks should be applied to the head and top-knot area of the sheep – not on the main body of the animal.  Because the top-knot area of the sheep is removed during shearing and placed with the tags and lower leg wool, any contamination by marking sticks and aerosol sprays will be confined to the lowest valued line of wool.   

As more U.S. wool is sold and exported around the world, the reputation and prices for all growers are impacted. With education and grower support the incidence of finding problematic paint brands in U.S. wool can be decreased. 

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If growers must use branding fluids the following recommendations are advised:
 
FOLLOW DIRECTIONS as listed on the container, adding to or heating the branding fluid can alter the scourability of the paint
If the fluid is too thick, place the can in warm water to reduce thickness. 
Never add solvents or thinners to branding fluid to “thin it” as this can change the chemical composition..
Do not directly heat the branding fluid container.  Heating the container can cause the branding fluid to change composition.

USE BRANDING FLUID SPARINGLY.  Excessive application should be avoided.  This includes large brands, “clumps” or “heavy blobs” of paint branding fluid on the animal.

Brand sheep to allow maximum exposure time to the weather.  Brands will fade and break down with exposure to the elements.  Branding immediately after shearing is recommended.
Brands should not be wider than 4mm (about ~1/4 inch) in thickness.