Cork is the outer bark of the cork oak, Quercus suber, and nearly all of it comes out of the western Mediterranean, around half from Portugal alone. What makes it worth having in a damp enclosure is suberin, the waxy polymer that is cork's largest single component at a little over 40 per cent. Extracted cork suberin has been shown in the laboratory, on a related oak, to hold back both white-rot and brown-rot fungi, which is a reasonable explanation for why a slab of cork outlasts every other piece of wood in a humid tub, although nobody has run that test on a terrarium. In use it is doing three jobs simultaneously. It is a hide, and a colony will gather underneath it to sit out the day and to moult somewhere they feel covered. It creates a microclimate, holding damp against its underside while the top face stays dry, so a piece laid across the moisture gradient hands your animals a choice they can act on. And it gets grazed. Whether they are taking the cork itself or the film of algae and microbes growing over it seems never to have been checked, but a piece that has been in a busy enclosure for a year plainly shows the wear. It works the same way for millipedes and for roaches, where it doubles as a climbing surface. Correcting our old advice This page used to say bake it at 200°C for half an hour and stay below 300°C to keep clear of cork's ignition point. We have taken that down. Cork begins breaking down from around 180°C and is well into it by 290°C, so 200°C already sits inside the range where the material is being damaged, and 300°C is not a safety margin either: dry cellulosic material can catch from about 250°C, and lower still if it is held hot for a long stretch, which is exactly what an oven does. Cork is also a natural insulator, so the core takes a long time to come up to temperature, which is precisely why oven treatment tempts people into leaving it in too long. Use a low oven and watch it, or put the piece in the freezer for a few days instead, which deals with mites and their eggs perfectly well and cannot set fire to your kitchen. Shop-bought cork is low risk to begin with. Cork is a natural product and pieces are picked as they come, so thickness and shape vary and some are chunkier slabs than others. Worth bearing in mind if the enclosure is a shallow one. The small size suits starter tubs and compact setups, or works as one hide among several in something bigger. Lay it so part sits in the damp end and part in the dry, and leave it alone after that. Pair it with leaf litter and lotus pods for cover at ground level, or step up to the cork bark tube if you want something the colony can get inside as well as under.
