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Trouble Shooting Guide for vacuum-formed refractory fiber shapes
Here are some typical problems with vacuum-formed shapes:
 Problem Possible Causes Probable Remedy
soft and weak pieces too little starch
  • check weight or volume of starch used
  • increase starch in formulation

bacteria eating starch; unusually smelly effect

  • clean out system with Clorox to kill bacteria and treat water like swimming pool to keep bacteria free


increased fiber size, length and/or diameter
  • chop fibers longer or add some chopped fibers to formulation
  • consult with fiber supplier



too high colloidal silica to starch ratio
  • optimize by using less Levasil FO1440 in formulation or use bigger particle size Levasil FO2040 for greater strength


starch inconsistency
  • try a different pallet and lot number
filler content
  • check weight and size of filler used
if using Wesil CS binder too little binder
  • check weight added; try 10% more
filler content
  • check weight, size and quality of fillers
errant Wesil CS
  • try a different pallet (1000#/batch)
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longer forming time

smaller or shorter fiber


  • try fiber from different pallet
  • consult with fiber supplier
filler too fine, too much filler
  • check weights and filler analyses
  • use coarser filler, 100-120 mesh preferred. Try 48 or 35 mesh to open it up
too much binder
  • check weights and ratio of silica to starch
  • reduce starch or Wesil CS by 10%
clay in formulation
  • don’t use clays with Wesil CS
  • in general clays like bentonite increase forming and drying time
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rough back side over floccing; slurry too concentrated
  • reduce starch, increase silica to starch ratio
  • run lower fiber content in slurry
  • use less Wesil CS
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slow drying poor de-watering
  • reduce silica to starch ratio in formulation (less colloidal silica)
  • if using Wesil CS, reduce amount 10%
clay in formulation
  • clay tends to hold water; check weight used. Use less.


air circulation in oven
  • drying above 250°F degrades starch; low humidity gives fastest drying so much air must be vented early in drying cycle (with good circulation)


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poor floc, cloudy water

too little binder


  • check to be certain correct amount of colloidal silica was added
  • increase colloidal silica by 10% to see if floc improves
starch inconsistency
  • try a different pallet, different lot
  • if pre-dissolved, make up fresh batch


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high temperature shrinkage wrong fiber
  • use higher temperature fiber
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reformulation wrong binder
  • use larger particle colloidal silica or Wesol alumina binder
wrong filler
  • use mullite or alumina filler (high alumina content)
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If you still have a problem and would like expert technical assistance, give us a call or follow this link and describe your problem. We'll get back to you to help you determine a solution.
Tech Help

WesBond Corporation

1135 East 7th Street

Wilmington, DE  19801

phone (302) 655-7917 fax (302) 656-7885 

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