I just acquired a 10' x 1' porcelain Standard Oil Company sign that was buried in dirt for the last 30-40 years. There is minimal rust, but a lot of "crud" from being buried for so long. I have been washing with soap and water, but some of it is really stuck on. I currently have it covered with damp towels to try to soften the crud.
I thought about using my power washer, but don't want to mess it up.
Any ideas would be appreciated.