An old, dirty oil lamp can be dangerous as well as unattractive. Waxy deposits on the inside glass can dull its appearance and get soaked up into the wick, making it burn unevenly or with too much smoke and soot. Keep the inside of your oil lamp as clean as the outside to ensure continued smooth functioning and safe operation. Clean oil lamps by first pouring out the old oil and disposing of it as you would motor oil. Never pour old oil down a sink or toilet.
Remove the oil lamp's globe, wick and the cap on the oil reservoir, and set them aside to be cleaned separately. Pour the old oil out of the reservoir into a jar or plastic bottle, pouring it through a small funnel, if necessary. Screw the lid tightly onto the container.
Pour a tablespoon of granular dishwashing detergent into the reservoir. Add very hot, but not boiling, water until the reservoir is two-thirds full. Cover the top of the reservoir and swirl the water to dissolve the detergent and coat the entire inside of the glass.
Scrub the inside of the reservoir with a bottle brush to dislodge deposits and oil film. Pour the soapy water out and refresh it the same way, except this time fill the reservoir to the top. Let the soapy mixture sit in the reservoir overnight.
Rinse the reservoir with hot water until it runs clear when you pour it out. Run your finger along the inside. If it's squeaky clean, you're done. If not, proceed to the next step.
Spray the inside glass with window cleaner and rub with a soft cloth wrapped around the bottle brush. Rinse with hot water and let the lamp air dry.
Refill the lamp with fresh oil and reattach the cap, wick and globe.
Don't use boiling water on a glass reservoir, or it may crack or shatter the glass.
Do not use paint thinner or toxic solvents to clean oil lamps. They work, but disposal, fumes and flammability of these solvents isn't worth the risk.