Care Of Pressure Canning Equipment To preserve low-acid foods which are safe, good tasting and nutritious, you need to correctly use equipment which is well-maintained and in good operating condition. Safety Vents or Petcocks: - Be sure the vent is clear and unobstructed. Use Q-tip or cotton string to clean. - Be sure vent tubes are screwed tightly into lid. - If it is a model with vent under the handle, be sure the lever is moving freely. - If it is a model with a petcock, be sure it opens and closes freely, either by screwing or flipping the lever up and down. - If there is a film from hard water on the petcock, and it can be unscrewed from the lid, soak the parts in vinegar, then wash and dry. - A ball and socket type petcock can be cleaned with silver polish. Safety Overpressure Plugs: - If it is a metal alloy or composition metal plug that screws into the lid, do not try to remove it. - If it is a rubber plug, use the thumbnail test to see if the rubber is still pliable enough. If pressure with thumbnail leaves a permanent dent in the rubber it is too brittle for safe use and should be replaced. - If either type of plug has been blown out by overpressure in the canner, it must be replaced by a new plug. Do not try to reuse the plug that blew out. Gaskets: - Soak gasket in hot water for an hour to soften before the first use of the season. - Insert gasket into its groove in lid. If it is either too shrunken to fit to the edge, or too stretched to lie smoothly in the lid, it must be replaced. - Use thumbnail test - if pressure with thumbnail leaves a permanent dent in rubber, it is too brittle and should be replaced. Rubber safety plug should be replaced at the same time, since it will probably be too brittle also. Pressure Gauge: - Have dial and pop-up gauges tested every year before canning season at your local Cooperative Extension Office. If it is inaccurate it must be replaced. - Check entrance port and carefully remove any debris that may have accumulated. - Be sure gauge is screwed firmly into lid. If it attaches with a nut on the underside of the lid, be sure the nut is tight. Weighted Pressure Regulators: - Have no moving parts so there is no need to have them tested for accuracy. - Be sure they are clean, with no debris or food residue encrusted especially in the sockets where the weight fits over its vent. - Be sure the entrance port and vent pipe are open and unobstructed. - Be sure there are no nicks or damage to the weight or to the tip of the vent pipe where the weight fits. Canner Lids: - Be sure handles are securely attached. - Be sure gasket fits smoothly into its groove in the lid. - Set lid on canner and turn to lock it into place. It should turn on smoothly and easily. - If it does not turn on easily, check to be sure gasket is properly seated in its groove. Adjust if necessary. - If the gasket is properly seated, check the lid. If the lid is warped or bent, it might be replaceable. Contact the manufacturer. If it is an old model or no longer manufactured, there may be no way to continue using it as a pressure canner. It may be used as a regular pot for cooking. If this is the case, remove the gasket, and if possible open or remove the gauge and overpressure plugs or petcocks, to avoid the possibility of pressure buildup. - If there is no visible problem but the lid continues to be tight, a small amount of petroleum jelly or cooking oil may be applied to the gasket to lubricate it. Canner: - Be sure there is a rack in the canner. - Check the bottom for flatness. Older model canners may warp if overheated. If the bottom is not flat or the canner will not sit flat on the heating element or burner of the stove, it should not be used for canning. Warped canners may be used for cooking. Once warped, the damage can not be reversed. - Put 1 inch of water in the canner, close the lid, heat the water and pressurize the canner. Check to see if steam is escaping at any point other than the petcock or safety vent. - If steam is escaping around the gasket and it seems to be properly in place, a small amount of petroleum jelly, or cooking oil, may be rubbed around the gasket. This will soften it and help it to seat more securely. Too much oil or jelly will over-soften the rubber, and will leave a sticky residue on the canner. - With weighted gauge canners, if the weight only hisses continuously and does not rock or jiggle intermittently as the manufacturers' directions specify, check to see if the stove is level. This type of weight must hang in a centered position on a vertical vent. If the stove is not level the weight will not hang properly and steam will escape in a continuous stream from the side, and pressure will not build up properly. - If steam is escaping around the base of any of the vents (dial gauge, weight vent, safety vent, petcock) where they screw into the lid, and if you can screw them out of the lid, the threads can be wrapped with plumber's tape to seal them. Plumber's tape is a stretchy, non-sticky silicon tape used to seal threads. It is available in small rolls from a hardware store. Be sure to wrap the tape in the right direction, so that when you screw the vent back into the lid, the direction of the turning does not unwrap the tape. Canner Use - Follow manufacturers' directions for use of your particular model. - Use canner on the appropriately sized burner. A canner should not hang over the edge of the burner by more than 2 inches on either side. - Be sure to center the canner on the burner. Some ranges do not allow enough space to center a large canner on rear burners. - Be sure lid is securely locked on (turned on, or screwed down). - If your canner has six or eight large screws and wing nuts to close it, screw them down in opposite pairs. If there are six, screw numbers 1 and 4 down part way, then 2 and 5, then 3 and 6, then return to the first pair to finish tightening continuing around the lid. - For all models, be sure to vent the canner for 10 minutes on high heat with a full stream of steam escaping. This is necessary to remove air from the canner. Air remaining inside will lower the maximum temperature achievable, and may cause underprocessing of the food. After the 10 min. venting, close the petcock, or place the safety weight or weighted pressure regulator on the vent. Allow the pressure to build to 10 psig, or to 5 or 15 psig if you are processing at those pressures. (psig means Pounds per Square Inch by Gauge, the measure of pressure.) Be sure that you use the proper time for the pressure level that you are using. Check the new USDA Home Canning Guide for safe recommendations. - When canner reaches the specified pressure, begin counting the processing time. - Reduce heat gradually to maintain the pressure without over-pressurizing. With a weighted pressure regulator, leaving the heat on too high will not increase the pressure, but will cause excess steam loss from the canner, since steam will be escaping continuously. Surpassing the specified pressure in a dial gauge canner will result in soft, mushy or darkened food, and excessive vitamin loss. - If the pressure drops below its proper level during processing, increase the heat to bring the pressure back up, then begin the timing over again from zero, for the full specified time. - Never run cold water over a canner to cool it. While newer, lightweight aluminum canners will not warp the way old ones did, the full, slow cool-down time is necessary for adequate process time. Shortening the time by cooling the canner with water is unsafe. In addition, excessively rapid cooling may cause jars in the canner to crack or explode as the pressure in the canner drops more rapidly than the pressure in the jars. - When the pressure has dropped to zero, wait another 1 minute before opening the canner. On some models the pressure drop will be visible when the overpressure plug drops back into the lid, the rubber plug is no longer bulged, or the dial gauge will read zero. Smaller canners will take at least 30 minutes to cool, larger ones may take over an hour. - Open the petcock or remove the safety weight carefully and wait until any rush of steam has stopped. Then open the lid and tilt the back edge up first, so that it directs the steam away from your face. - Remove the jars immediately. Do not leave jars sitting in a hot canner overnight, spoilage may result. Canner Storage: - It is acceptable to leave clean water in the canner if you are going to be canning again the next day. However if much juice from the jars escaped and the water in the canner is colored it should be discarded. - Turn the lid upside down and rest it on the canner. The weight of the lid should not be resting on the gasket during storage as it could deform it. - For long-term storage at the end of the season, wash and dry the canner well. Be sure all the parts (safety weight, rack, etc.) are in the canner. A few crumpled newspapers in 1the canner will absorb moisture and odors. - If you unscrew the gauge or vents, coat the threads lightly with petroleum jelly to prevent rust and make them easier to replace. - Coat the gasket very lightly with petroleum jelly or oil. Burpee, Health, National Victory and Dixie canners are no longer manufactured, and no parts or service are available for these canners. Parts and service are available for Presto, Mirro and All American, and for some models of National Presto, Kwik Kook, Steamliner and Maid of Honor. If you need further assistance or have other problems, contact your local Cooperative Extension Office. If you are thinking of buying a canner at a garage sale, check to be sure you can open and close the petcocks. Look for stains of drips down the sides or on the lid near the vents, they may indicate that the lid does not seal or leaks steam all the time. Check that the lid twists on and off easily. Check the condition of the gasket. Check that the base is flat. A rounded base indicates that the canner is warped. Check that there is a rack. Buying any of the models listed above as having parts and service available is a much better bet than one of the older ones. Prepared by Mary A. Keith, Foods and Nutrition, August, 1991 Revised by M. Susan Brewer, Foods and Nutrition, June, 1992 EHE-704