在一文章中同时出现三个有盖子（塞子、封口）的词，分别是cap\lid\closure，还出现了metal band,metal lid等让我困惑的词，下面是相关段落。请大家帮帮我，这里先谢过了！
Closures
There are three types of closures for glass jars. Be sure to follow the sealing directions that come with each type of closure. Some general suggestions about two of them are given in the following paragraphs.
Three-piece Cap. This fits a deep-threaded jar with or without a shoulder. The metal band holds the glass lid in place during processing and cooling. Remove it when the contents of the jar are cold, usually after 24 hours. Use a new rubber ring each time.
Two-piece Cap Use the metal lid only once. The metal band is needed only during processing and cooling . Do not screw it farther after taking the jar from the canner. Remove the band after the contents of the jar are cold, usually after 24 hours.
Lids
When the first edition of STOCKING UP came out in 1973 , there were only three companies producing lids for the popular two-piece cap . Now, in 1977, after the canning lid shortage of a few years ago, there are at least 15 companies producing lids . Most of these new lids are fine and work well, but after testing in our Fitness House Experimental Kitchen, we did discover some types of lids that did not hold the seal as well as they should.
We suggest that when buying lids you check the inner sealing ring to see that it is uniform in thickness and covers the entire area of the lid that will come into contact with the jar. One thing to look for in a good lid is a series of concentric circles, at different levels . This form of construction allows the vacuum to pull down the middle part of the lid, forcing the outer ring into good contact with the jar. Lids that don not have these rings tend to have the entire lid bow under pressure. , still giving a seal, but one that is much more fragile , as less of the lid is in contact with the jar. Another point to look for in a good lid is the quality of the coating on the inside of the lid. Lids that do not have a thick, uniform coating may corrode much more quickly than quality lids . One last feature we found desirable is a small dimple in the middle of the lid. These dimples give the lid a louder clicking sound when a proper seal is made and make it easier for you to see that the lid is pulled down, the sign of a good seal.
Paradoxically, when buying canning lids you may well not get what you pay for. Large established companies are able to sell quality lids at a low price due to the size of their production. Some of the smaller companies therefore sell less quality, for more money.
If you are in doubt about the quality of the lid, look to see who makes it . If the company lists their name and mailing address on the package you can write them and ask for test results. Ask your local extension service’s home economist if there are any tests results available on the lids. No government agency is responsible for the quality of lids. Several government agencies test the sealant used in lids for safety, but no one agency is responsible for seeing that lids work well.
这几种盖子搞的我晕晕晕
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