Article in English: Slowly but surely, any rubber object, be it your car windshield wiper blades or the elastic waistband of your favorite pajama pants, will harden over time.  Evidence of white or colored substances on the rubber can be one indication of a chemical reaction taking place.  Natural rubber has poor resistance to both ozone and UV light, as well as to petroleum oils.  Additionally, temperatures below -60°F (-51°C) or above 220°F (104°C) will degrade it quickly, while temperature extremes in general will facilitate long-term degradation and hardening.  Rubber stretches and flexes because it is made up of long, tangled molecule chains that can be straightened out under tension.  Degradation of these molecular chains can occur from repeated or excessive tension (think of frayed or over-stretched rubber bands), or by exposure to elements like those noted above. Cracked rubber will remain cracked even when it’s softened. Once cracks form, your only options will be to try out a rubber patch kit or to simply replace the rubber object.  There is no miracle cure by this point. One point worth making here is that common softening methods — heat and oils — actually damage the rubber in the process.  So, every time you do soften up a stiff rubber gasket or shoe sole, you are also contributing to its eventual demise. There is only so much you can do to keep oxygen, temperature fluctuations, and light away from rubber, but wiping away residue can help keep deteriorating oils from damaging the object.  Clean rubber objects with only warm water and a clean cloth when possible. If necessary, use a mild detergent and rinse it away completely. Solvents found in cleaners can degrade or even dissolve rubber.  Avoid washing clothes with elastic waistbands more than needed, and don’t use hot water. If possible, remove as much air (and thus oxygen) from the container as you can before sealing it.  Placing rubber items in zip-close bags and using a straw to suck out most of the air can noticeably delay the hardening process.  If you’ve...

Summary in Indonesian:
Periksa benda berbahan karet secara teratur untuk mengetahui pengerasannya. Periksa tanda-tanda kerusakan pada karet. Jaga kebersihan benda berbahan karet. Simpan benda berbahan karet dalam wadah kedap udara untuk menunda pengerasannya. Letakkan wadah dalam tempat yang kering dan gelap.