Pennies seem to have a knack for getting tarnished quickly. Luckily, they are easy to clean with common household items. Lemon juice and vinegar are two such items that are well known to give pennies back their coppery lustre. But which works better---lemon juice or vinegar?
Lemon Juice vs. Vinegar
Ultimately, lemon juice will clean pennies better than vinegar, though both liquids are viable cleaning options for copper. Vinegar has a pH level of 3.0, while lemon juice has a pH level of 2.3. This means that lemon juice is a slightly stronger acid than vinegar. The stronger the acid, the better it will clean copper pennies.
Why It Works
Copper is exposed to air and elements over time, and it eventually oxidises, forming copper oxide. Copper oxide is that black, tarnished film coating the penny. The acid in the vinegar and lemon juice works only on the copper oxide, dissolving it to reveal the original copper lustre underneath the film.
Find 6 to 10 tarnished pennies of your own to see how lemon juice pairs up to vinegar as a penny-cleaning product. Fill one small cup with 5% white vinegar and another cup with lemon juice. Place half the pennies in the vinegar cup and the other half in the lemon juice cup. Leave the pennies in their respective cups for at least 30 minutes. Drain, rinse and dry the pennies from both cups and then compare which solution cleaned the pennies better.