Tree sap on a street bench is sticky, attracts dirt, and looks terrible. The good news is you do not need harsh chemicals or heavy equipment to clean it. Here is the procedure I would follow.
Start by checking what the bench is made of. Most street benches are wood, metal, recycled plastic, or concrete. The method is similar for all of them, but wood needs a gentler touch because rough scraping can damage the surface or push sap deeper into the grain.
Gather your supplies: warm water, mild dish soap, a bucket, a soft cloth or non-scratch sponge, a plastic scraper or old credit card, and either rubbing alcohol or hand sanitizer. If you do not have alcohol, a little vegetable oil or mineral oil can also work.
First, clear off any loose dirt, leaves, or debris from the bench. Then test your chosen sap remover, especially alcohol or oil, on a small hidden spot to make sure it does not discolor the material.
Now tackle the sap. Mix a few drops of dish soap into warm water. Soak a cloth or sponge in the soapy water and press it onto the sap for a minute or two. Heat and moisture help soften the sap. Then take your plastic scraper and gently lift the sap from the edge. Work in one direction to avoid smearing it around. If the sap is thick and hardened, apply a little rubbing alcohol or hand sanitizer directly to the spot, wait about thirty seconds, and then wipe or scrape. Alcohol breaks down the sticky resin quickly.
Once the bulk of the sap is gone, wash the whole bench with the warm soapy water. Use a soft cloth or non-scratch sponge. For wood benches, scrub with the grain rather than in circles. Rinse thoroughly with clean water, using a bucket or hose if you are near a water source. Dry the bench with a clean towel so it does not stay slippery or develop water spots.
If a hazy or sticky film remains, put a small amount of vegetable oil or mineral oil on a cloth and rub the area gently. The oil dissolves leftover sap. Then wash the bench again with soapy water to remove the oily residue, rinse, and dry.
For wooden benches that have lost their protective finish, consider applying a wood sealer or outdoor furniture wax once the bench is completely dry. This will not stop sap from falling, but it makes future cleanups easier and protects the surface.
One last tip: if the tree above is still dripping sap, cover the bench or move it temporarily if that is an option. Otherwise, plan to wipe it down every week or two during sap season. A quick soapy-water wipe before sap hardens is much easier than a deep cleaning later.
That is it: patient soaking, a plastic scraper, some alcohol or oil, and soapy water. No need for a pressure washer or a paint scraper.