Remember those science experiments you did as a kid? Perhaps your favorite part was the magnets or maybe it was even the dissecting, if you were a purist or a contrarian. One particular science experiment I remember well had to do with two very common place things: a penny and some Coke.

The preparation for the experiment was one of the best parts. For the penny you’d have to come up with the dirtiest grubbiest coin you could find. The more tarnished the better. Grocery store parking lots were good places to look, as were the crevices in the couches. The best penny was the one that only revealed its pennyhood by size—all the embossed features were begrimed beyond recognition. The Coke was fun too—as kids we hardly got to drink the stuff. Its sugary fizziness was associated with spring soccer games and other kid’s birthday parties, and now science.

I remember the instructions well. You were supposed to pour a good amount of the cola into a glass and then carefully drop your filth-encrusted penny into it. Then you waited. A day or two later you’d look at the penny in awe. It was shiny and bright, restored to near mint quality. The Coke had wrought a miraculous transformation.

Naturally, of course, the application at the time was that of a dreadful warning: beware lest the cola’s acid eat away your teeth and stomach.

But now the experiment holds a different significance for me. I think it is because sometimes I feel like a penny myself, caked by the bad choices and decisions I’ve made. Encrusted with the filth of life experience. It’s as if at a certain point I fell (or jumped) our of someone’s pocket and rolled into the street in search of greater space or fell into the couch seeking its mysterious and inviting confines. To me the penny symbolizes a perfectly minted person—not in the image of Lincoln, but in the image of God—that has lost its brightness. Just as the cola cuts through the grime, so God’s grace cuts through my calloused heart and brings beautiful painful bright redemption. It takes time and the wearing away of the caked-on layers can hurt bad, but what was meant to be can be again.

What can wash away my sin? Nothing but the blood of Jesus.