Knowing what your silk bedding is made of is crucial if you are seeking a duvet that will do what you want it to do. Long fiber mulberry silk is what you should be seeking in a duvet. The majority of other types of silk will not be as nice as long fiber mulberry silk will be. This type of silk does come with a hefty pricetag though. It is pricey, but as you know, you typically get your money's worth. The silk duvets that are cheaper are usually filled with a combination of silk and polyester, or chopped up strands of silk which are basically cheaper pieces of silk that aren't suitable to be used for any other purpose. A good quality silk duvet will include a small zip for inspection purposes, where you can look closely at the quality of silk that is inside the duvet. If your duvet is lacking this inspection zip, you should probably ask yourself what exactly is in your duvet.
In Britain, there is no standards tog rating used for silk duvets. This leaves the market somewhat in turmoil since certain suppliers will suggest one thing, while others may recommend something completely different. The tog rating system is devised by calculating the grams of silk per square meter of fabric. A duvet that is filled with 250 gsm of silk would be equal to a 2-4 tog. A duvet that is filled with 400 gsm would be equal to a 7-9 tog, and a duvet that is filled with 600 gsm would be equal to a 10-13 tog. A lot of suppliers will provide a combination duvet that would be bot a 250 and a 400 gsm duvet that connect together. You can often find a good deal or a discount when you buy a combination duvet set.