I only read about “spiking” in polymer clay books which advise you to regularly check the temperature during the curing process. As our normal oven in the kitchen takes ages to warm up and I don’t want to bake polymer clay in it,we bought a table top oven from Morphy Richards, which was on sale. I also have a professsional thermometer for the oven. However the oven is not super accurate and after warming up the temperature rises quickly and way over the required 110 C for Fimo (or 130 C for Premo) so normally when I bake I tend to check on the oven and keep changing the temperature. It also goes down quickly so I have to increase it again.