This lovely mug wooden mat was made from some English Ash, sourced from the National Trust at Ashridge (other timber sources may be used). It has about 5 coats of Hampshire Sheen's Citrus Oil finish. I use one of these daily, and whilst no finish is going to be 100% water resistant for life, it does a good job, although of course like all wood, water sitting on the surface will change the look & feel of the surface, and some fluids, such as fruit juices/wine etc. may stain the item. Note: This is item is made of wood, no wooden item can be regarded as "heat safe", although in my testing, hot mugs of coffee etc. are OK.