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Chemtempering Photochromic Salt
Bath Temperature Guide

WHEN TO
CHECK THE TEMPERATURE

Routinely and.....

  • 24 hours after initial filling.
  • Once molten salt temperature is  reached, prior to loading lenses.
  • After every addition of fresh salt, once the temperature has stabilized.
  • 24 hours after complete refill.
HOW TO
CHECK THE TEMPERATURE
  • Use a calibrated thermometer.
  • Insert directly into salt bath.
  • Check several places across bath.
WHAT
TEMPERATURE RANGE
IS REQUIRED
  • 16-hour photochromic bath:
    395 - 405 C (743 - 761 F)
  • 2-hour FAST photochromic bath:
    445 - 455 C (833 - 851 F)
  • 16-hour White Crown/fixed-tint bath:
    445 - 455 C (833 - 851 F)
  • If temperature is outside that range,
    MAKE ADJUSTMENTS AS DETAILED BELOW
HOW TO
ADJUST THE TEMPERATURE

If the Temperature is too high or too low

  1. Reset temperature control by the appropriate amount to correct the bath temperature.
  2. Wait 2-4 hours.
  3. Re-measure temperature with thermometer.
  4. Repeat Steps 1-3 until temperature is correct.

PLEASE NOTE:

  • Consult manufacturer's instruction manual for information on how to adjust temperature of the chemtempering unit.
  • Over time, thermocouples on chemtempering units may become less sensitive and allow chemical bath temperatures to become too hot. Eventually, they will need to be replaced.
Problem Probable Cause Suggested Correction
Hazy surface
  • New bath - not cured for long enough before use
  • Polish lenses to remove haziness.
  • Allow bath to cure for at least 24 hours. Place no lenses or dummy lenses in bath during this time.
Hairline
surface cracks seen after chemtempering
  • Salt contaminated and/or pH too high
  • Bath temperature too hot.
  • White Crown or fixed-tint lenses in photochromic bath.
  • Replace salt.
  • Check bath temperature with accurate thermometer and correct temperature.
  • Discard lenses and redo in proper bath.
Excessive breakage
during
drop-ball test
  • Edging flaws.
  • Insufficient grinding and/or polishing on concave side of lens.
  • Bath temperature too hot or too cool.
  • Check edging wheel and retrue or replace.
  • Check generator wheel and retrue or replace.
  • Increase fine grind time.
  • Check bath temperature with accurate thermometer and correct temperature.
Pitted
lenses
  • Bath temperature
    too hot .
  • Check bath temperature with   accurate thermometer and correct temperature.
Spotted
lenses
  • Lenses not thoroughly cleaned before tempering.
  • Lenses were allowed to drip dry, resulting in spotting before they were chem- tempered. Tempering enhanced spots.
  • Make sure lenses are thoroughly cleaned before tempering.

  • Make sure lenses are thoroughly cleaned before tempering. Do not allow lenses to drip dry.