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Short castings or Incomplete castings
Rough castings
Castings are too tight
Castings are too loose
Porosity
Short castings or Incomplete castings
  Check wax thickness
 
Should be 0.3mm minimum. Bridgework is typically waxed to 0.5mm minimum.
   
  Check burnout temperature
 
Should be within 25°F of our recommendation.
If everything else checks out, raise in 25°F increments.
   
  Casting force
 
For spring wound machines, typically use 2 turns for C&B gold and high gold PFM, and 3 turns for Au-Pd, Pd-Ag, high palladium, and Ni-Cr.
While miscasts due to insufficient force are more common, miscasting can result from excessive force due to mold gas back pressure.
Broken arm should swing easily.
   
  Spruing
 
Smooth crucible formers improve castability.
Sprue for metal flow.
No more than ¼" investment over the tops of patterns.
   
   

Rough castings
 
Debubblizer must be dried prior to investing. Wet debubblizer can contribute to investment breakdown.
ONLY mix investments with special liquid and DISTILLED WATER. More investment related problems are caused by the use of tap water than you would possibly believe.
Check burnout rates, temperature and hold times. Watch out for excessively slow or fast rates, extra long hold times, or extreme temperatures - all can contribute to investment breakdown.
Check investment mixing technique. Specifically, spatulation time should be within recommendations (typically 1-2 minutes). Special liquid concentrations should be within recommendations as well.
Follow recommendations for setting time. Do not rush setting time, and do not remove crucible former prematurely.
Look for trends. For example, are all castings rough or just some? Which ones? Those invested in the morning or the evening? Singles or bridges? Those from small diameter rings or large ones? etc.

Keep separate mixing bowls for gypsum and phosphate materials.

Is the inside rougher than the outside? Try a different die lube.
If the problem came on suddenly, make a casting from all new metal. You may have a contaminant.
If the problem came on suddenly, obtain a new box of investment. We do occasionally hear of the proverbial "bad batch" of investment or liquid.
   
   
Castings are too tight
  Increase the concentration of Special Liquid.
 
Decrease the total liquid volume 0.5ml.
Use an extra layer of ring liner.
   
   
Castings are too loose
 
Decrease the concentration of Special Liquid.
Increase the total liquid volume 0.5ml.
   
   
Porosity
  Shrinkage porosity
irregular in shape, usually in the thicker sections and up near the sprue. Spongy appearance to the metal.
 
Improving the spruing will solve 95% of the shrinkage porosity problems that technicians encounter.
Excessive burnout temperature will contribute to shrinkage porosity.
 
Gold  C&B alloys 900-1200°F
Silver-Palladium C&B alloys 900-1200°F
Gold-platinum PFM alloys 1300-1400°F
Gold-palladium PFM alloys 1400-1550°F
Palladium and palladium-silver PFM alloys 1400-1550°F
Excessive casting temperature will contribute to shrinkage. Improve the torch adjustment and check your casting indicator.
   
  Gas porosity
round in shape, no specific location on the casting. Frequently subsurface.
 
Check your torch adjustment and tip condition. Poor adjustment or flame condition is the most common cause of gas porosity.
Preheat crucible with torch prior to placing alloy in the crucible.
Replace worn crucibles.
Always add fresh metal when casting.
Ensure complete burnout.
Do not overheat. With most alloys, we cast when the alloy becomes a ball that no longer sticks to the sides of the crucible when we jiggle the casting arm. With Castell and State, we cast before the alloy forms a ball. Nickel-Chrome alloys should be cast after the ingots slump (never break the oxide on Ni-Cr!).