Thinset residue on outdoor cushions can be stubborn, but with the right approach, you can restore them to their original condition. Here’s a step-by-step guide to effectively remove thinset residue:

1. Scrape Off Excess: Use a plastic scraper or putty knife to gently remove as much dried thinset as possible without damaging the fabric.

2. Vinegar Solution: Mix equal parts white vinegar and water in a spray bottle. Spray the solution onto the residue and let it sit for 10-15 minutes to loosen the thinset.

3. Scrub Gently: Use a soft-bristle brush or sponge to scrub the area. Avoid harsh scrubbing to prevent fabric damage.

4. Rinse Thoroughly: Rinse the cushion with a hose or damp cloth to remove any remaining residue and vinegar solution.

5. Repeat if Necessary: For stubborn spots, repeat the process or apply a small amount of baking soda paste (baking soda mixed with water) for extra abrasion.

6. Air Dry: Let the cushion dry completely in the sun before using it again.

For tougher stains, consider using a commercial adhesive remover, but test it on a small, hidden area first to ensure it won’t discolor the fabric. Regular maintenance and prompt cleaning can prevent thinset buildup in the future.