I use Dawn dish detergent and white vinegar in tap water just hot enough to get the pinecones clean, but not too hot to burn my hands. I use the scrub brush for stubborn dirt and sap.
I submerge my pinecones into the hot tap water.
Once they have drained on the towel, I put the pinecones on a cookie sheet covered with foil. I don't want the sap on my pan!
I put them in the oven on about 225 degrees for an hour, then lay them out to finish drying in the air. This is when my house usually looks like a pinecone factory. And talk about an amazing aroma permeating throughout my house! I do open the windows and keep extra fans on low to medium, circulating the air during this time. I recommend you do the same!
Once the pinecones open, I'm ready to start crafting!
I paint them and make floral stems and use these for wreaths as well.