COMMON PROBLEMS AND SOLUTIONS

PROBLEM	CAUSE	REMEDY
Plate tends to stick to mold, is gummy on removal	Rubber not fully cured.	Cure rubber for full time and temperature recommended.
	Molding press temperature too high or time in press too long (overcure).	When the heat history (time and temperature) is too high, some natural rubber stocks will revert. (cure then soften).
	Molding press temperature too low.	Raise press temperature. Also be sure press has been on long enough to reach equilibrium before starting.
Plate and/or letters not filled completely	Insufficient charge.	Use rubber thickness within 10% of plate thickness desired except: a) Type areas 10 to 15% less than desired thickness. b) 100% solids use at least 20% more than desired thickness.
	Insufficient dust.	Redust face before molding. Store rubber in a cool dry place.
	Press closing too quickly.	Close press slowly to let air escape.
	Old or partially setup stock.	Check age of uncured rubber.
	Molding press too hot.	Check for correct and uniform temperature on platens.
Premature wear with pitting and/or swelling	Effect of ink or cleaning solvents on incorrect rubber compound.	Use proper compound for the solvent being used.
Minute cracks in one direction on rubber surface.	Ozone exposure.	Store plates in a cool, dry, dark place in a sealed black polybag.
Plates uneven or high centers.	Mold may be overloaded.	Reduce amount of rubber.
	Platens not parallel.	Have platens adjusted.
	Old or partially setup stock.	Check age of uncured rubber.
	Rubber doesn't flow well.	Use rubber with faster flow.
Plate curls when molding or after stripping from the matrix.	Old or partially setup stock.	Check age of uncured rubber.
	Excessive molding pressure.	Use only enough pressure to ensure tight bearers. Try using less pressure to reduce initial platen pressure.
	Press closing too slowly causing rubber to partially setup.	Close press faster. Do not use preheat.
Face rubber does not adhere to backup (grinding stock).	Rubber types are not compatible.	Select appropriate compounds.
	Old or partially setup stock.	Check age of uncured rubber.
Plate shrinks in storage.	Improper cleaning.	Use proper procedures.
	Solvent has extracted some of the plasticizer in the compound.	Use proper procedures.
Broken fabric in reinforced plate.	Old or partially setup stock.	Check age of uncured rubber.
	Compound is too stiff.	Use softer compound.
	Compound flows too much.	Use compound with less flow.
	Overloading.	Use less material.
Plate distorts and does not return to original size when stripped from matrix.	Undercure.	Press temperature too low. Cure time too short.
Face of the plate fills out but back has voids or depressions.	Insufficient rubber.	Use thicker rubber or add slugs where needed.
	Air trapped between rubber and cover sheet.	Dust back side of rubber.
Rubber tears on removal from mold.	Mold too deep for desired plate thickness.	Leave sufficient rubber in background to furnish strength required.
	Angle on text too steep or undercut.	Remake matrix or engraving.