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Which Water Blocking Application Method is Best for Wire and Cable?

Water blocking yarn treatment

Advantages and Disadvantages of various Water Blocking Treatments and which is best for you. 

The critical reason for a wire and cable manufacturer to use a water blocking treatment in their product is to prevent access and dissipation of water and moisture throughout the cable.  When deciding on which treatment to use (i.e. gel, yarn, or powder based) in your cable, it’s important to consider the advantages and disadvantages of each application method.

Water Blocking Treatment Type



Gel Water Blocking

  • Complete prevention of moisture ingress as there are no gaps for water to fill
  • Provides additional layer of protection for wire or fiber
  • Best for areas that will see sustained water exposure or contaminants
  • Adds weight to cable
  • Can be messy to apply during manufacturing
  • Takes longer to prep cable for splicing as gel must be cleaned off

Powder Water Blocking

  • Lighter weight than gel
  • Multiple absorption capacities and speeds available
  • Once moisture is removed from contact, will dry and can be reactivated
  • Residue can contaminate equipment
  • Extra processing step needed to blow SAP into cable – In general, incorporated into existing process, no extra step required
  • Not meant for areas with extremely high water exposure or contamination

Yarn Based Water Blocking

  • Lighter weight than gel
  • Multiple absorption capacities and speeds available
  • Very little (if any) mess or residue during application into cables
  • Virtually zero prep time for splicing cables, yarn can be cut with scissors
  • Once moisture is removed from contact, will dry and can be reactivated
  • Can be applied using existing equipment for binding or inserting ripcords and fillers
  • Not meant for areas with extremely high water exposure or contamination
  • Must be activated by water exposure before offering protection


In a gel-filled cable, any space in the tube that is not occupied is filled with impermeable gel. Using this type of water blocking material can cause many challenges for installers in regard to time, cost and the mess created by the product. Having to clean gel from fibers can slow down the installation process and cause significant mess for technicians operating machinery, splicing or terminating this type of cable.   However, the effectiveness of a gel filled cable cannot be understated as gel water blocking completely prevents any kind of moisture ingress as there is no additional space for the water to fill. 

Super absorbent polymers (also referred to as SAP or slush powder) can absorb and retain extremely large amounts of a liquid relative to their own mass.  Powder based water blocking involves directly applying the SAP powder to a cable.   SAP powder is typically manufactured with a very fine particle size to maximize surface area available for water absorption.   Applying a water blocking treatment in this fashion, while effective, can result in the SAP powder getting all over the surrounding equipment and areas.

In contrast to the inefficiencies experienced with gel and powder based water blocking, there are also many benefits to the use of dry, yarn based, water blocking that are now widely recognized.   

With yarn based water blocking, yarns are used a carrier for SAP, instead of applying it directly onto and into the cable.  This allows the water blocking component to be applied to the cable with minimal shedding or contamination of equipment.  There are several methods available to apply SAP to yarns including solvent, aqueous or oil based treatments, either heat cured or applied under ambient conditions.  In addition, there are yarns available in which the yarn itself is made from a swellable fiber.  The absence of sticky grease or gel in yarn based water blocking offers a major reduction in time needed to prepare a cable for splicing, a decrease in cable weight, and no need for solvents or cleaners to prepare the cable for splicing.  Like powder based water blocking, swellable yarns only react in the presence of moisture and will form a seal to prevent additional water from entering the cable.  Performing a water absorbency test on these treated yarns will provide you with some of the test results needed to make the best choices of yarn and treatment for your product.  

The overall effectiveness of each type of water blocking treatment can only be measured by testing the final product.  If you need help determining the best type of water blocking method for your application, let us know and we will put our experience to work for you!  

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Water swellability test method

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