We have a young oak tree in our yard (well, young is relative when it comes to oak trees--it's about 15 years old, not too big yet), and this is the first year we've had noticeable numbers of acorns in our yard, so I decided to gather them up and get them all polished and sealed to use in a glass vase.
Here they are just picked up from the yard, nothing fancy--lots of caps had fallen off, and I found more caps than acorns, but for my first harvest, not too bad. I washed them off with some dawn to get all the dirt off. Then I let them sit outside for a couple of days in the sun to make sure they were good and dry. Then I put them in a zip top freezer bag and popped them in the freezer for a few days to make sure any bugs that might be crawling around in them were killed off. I've read tutorials where folks spread them out on a cookie sheet and baked them at low temperatures for a couple of hours, but I didn't want to mess around with that with such a small batch.
After I took them out of the freezer and let them warm back up to room temperature, I popped the caps off of the few that had stayed stuck on and polished up the acorns. Many of them had this scuffed up waxy build up (as seen in the photo above). So I took a soft paper towel and buffed them up. A real cloth might have worked even better, but the paper towel did the trick (as you can see in the photo below).
The transformation from wiping them off with the cloth was pretty impressive. Next I lined all of the acorns up sitting on their tops and neatly arranged the caps, so I could spray them with some clear acrylic spray. I chose a matte sealer so they would still look realistic instead of glossy. If you had some sad looking acorns you could even spray paint them some fancy color instead of sealing them.
I gave them two coats and let them dry for just a few minutes before bringing them inside to glue the caps on. I used a hot glue gun and spent a good while matching caps to acorns. Even with quite a few extra caps, they were tough to match when I got down to the last few acorns.
I filled the cap with glue and pressed it on. Easy peasy.
When they were all recapped, I threw them into this amber colored candle holder that I picked up for a few bucks on clearance at Target. It's not very full, so I'll definitely have to harvest again next year, but I'm on my way.