Most of todays' synthetics mimic real bristle very well. I just got a brush (¢heap) and wanted to verify it wasn't synthetic.
Method 1: hold a loose bristle above a flame. If it crinkles up and burns, it's bristle; if it melts, it's synthetic.
Method 2: soak a brush in warm, fresh water. Shake out excess water & show it to Suzette, my Siamese. If she shows a lot of interest in sniffing it and wants to play with it, it's bristle. If she gives a cursory sniff, then walks away, it's synthetic.
Method 1: hold a loose bristle above a flame. If it crinkles up and burns, it's bristle; if it melts, it's synthetic.
Method 2: soak a brush in warm, fresh water. Shake out excess water & show it to Suzette, my Siamese. If she shows a lot of interest in sniffing it and wants to play with it, it's bristle. If she gives a cursory sniff, then walks away, it's synthetic.