(1) (Balance) Lightweight rubber is in the unweighed part. The lighter rubber is in the lighter rubber. (This can ensure that two copies are normal, and the varnish is in one copy) Divide the five rubber sheets with varnish into two copies, two copies and three copies. (2) Add 1 good rubber into two blocks, and weigh to ensure that the rubber is in two or three blocks. (3) In 2, weighing can be known. (4) Divide the three into two parts, 1, two parts, 1 plus 1 good rubber, and weigh. If rubber is light, then 1 is enough. ⑤ If there are two, just weigh them again.