Instructions for the Fitting and Adjusting of Lenses
into Natural Horn Spectacle Frames
    General Rules:

  • Unscrew temples before inserting the lenses.
  • The temperature of the hot air blower should be 200oC / 400o F. Preheat before using. Do not use a salt pan, it will dry out the horn.
  • Heat the frame front for about 15 seconds constantly rotating the frame.
  • Take the frame out of the hot air blower, wait about 15 seconds.
  • Heat the centre part again for another 15 seconds, constantly rotating the frame.

Now the frame should be "lukewarm" and the lenses can be inserted. Spectacle frames made out of natural horn will never get as soft as plastic frames, even with further heating. Too much heat will cause the frame to shrink and/or the frame finish to be damaged. You will also burn your fingers.
Please note:
  Horn will only get hotter, but not softer!

Always use plastic lenses, never glass. Plastic lenses conform better with horn throughout temperature changes.

Choose lenses with base curves close to the curve of the frame, namely aspheric lenses, particular in cases of low prescriptions.

Sizing of lenses:
Never edge lenses too large. Lenses, which are edged too large, will break the horn. Edge lenses to size, check and resize accordingly. Often -0,20 mm is the correct size.

Lenses may feel small after insertion into the still warm frame, but horn shrinks a little when cooling and will tighten around the lenses. Two to three degrees of rotation right after insertion are in order. If desired cut a demonstration lens first to determine correct size.
Always remember to make a safety bevel at the apex of the edged lens.

Pre-grind the supporting lens, in order to control the size!
Remember to break/round the bevel point of the lens!

Adjusting the temples:
The temples should also be heated up in the hot air blower until the material is flexible enough for bending. Move constantly during the heating. Cool off temples in cold or running water to set adjustment.

Changing of inclination / pantoscopic tilt:
The material hardness does not allow one to change the inclination with the temples fitted - otherwise the material may break. You can change the angle of the hinge of the frame front using a hinge adjusting plier.

Never place horn frames or parts in an ultrasonic cleaner. Vibrations may cause horn to fracture. Use only soapy water for cleaning.

Upon request we will send you training material on which you can practice the insertion of lenses and the adjustment of spectacles.