I use SFIC bases and always microwave (not something I'm proud of, I'm just impatient :undecided ). Never had it negatively effect the lather, though. I usually microwave on 50% for about 3 minutes, stir, then at 70% in 30 second intervals with stirring until it's almost all melted. When there is just a few chunks that won't melt, I blast it at 100% for about 20 seconds and that gets it all. The reason I don't leave chunks is because if you add color, you'll have a white spot when you (or a customer) goes to use the soap. It's nothing really, but I don't like to see that. If you didn't get lather, and didn't add ANY other additives, then I am wondering what setting you microwaved on??