Bill G,

If the horn is beginning to crack from age or lack of humidity, you can repair or fix it to a point. The easiest method it to immerse the piece in mineral oil for a few days. Then take it out and let it dry. If time is a premium, place the piece in a pan over very low heat with mineral oil. Do not let it boil. Keep it in the heated oil for 4 to 8 hours.

After is has been "rejuvenated" you can repair any cracks and polish it.

Pete