Cleaning the Throat of Crucible
To eliminate a stoppage in the throat it is sometimes necessary to remove the mouthpiece and scrape out the throat, using a throat scraper to cut away the accumulation of dirt and dross.
The scraper sold by the Linotype Company is recommended for the purpose. Care must be used to get the throat clean. Hold a receptacle that does not leak up in front of the crucible mouth and force the plunger down by hand. This will flush the throat of any floating particles of dross.
Sometimes melted tallow, paraffin oil, or machine oil will open up the throat, by being used in the following manner: Dip the metal out of the pot to about an inch below the top of the well, remove the plunger, pour the melted tallow, paraffin oil, or machine oil into the well and replace the plunger. Cast a few blank slugs. After casting about six or seven slugs, fill the metal pot full of metal, recast blank slugs until you have filled the stick. The effect of the tallow or oil is to break up the dross and dirt into such fine particles, that whatever has accumulated in the throat will be forced out through the holes in the mouthpiece. This will cause considerable smoke in the room unless you have a ventilating system. Be sure to clean your vise jaws and mold after you have finished, for they will be covered with oil. It is not necessary to remove the mouthpiece for this operation so consequently considerable time can be saved. But if the throat is very dirty, this method will not work satisfactorily.