The most common causes of chemical off-flavors are heightened chlorine levels or bacteria and wild yeast in your brew. Secondary causes can be extended dry-hopping or elevated fermentation temperature.
If your finished brew has chemical off-flavors, you are better off trying again as they often result from processes that are irreversible later.
Most commonly, your brew tastes of plastic or antiseptic. In this case, phenols and chlorine are likely culprits. Certain chemical compounds, including chlorine and chloramine, present in tap water can influence the resulting taste of your beer.
If the chemical off-flavor resembles a solvent, like paint thinner, the fermentation temperature was probably too hot.
If your brew has a chemical or plastic taste, unfortunately, you probably need to start fresh.
1. Test and treat your water for chlorine. 2. Before starting on your brew, make sure to sanitize properly! 3. Finally, during fermentation, pay attention to the recommended temperature range in your recipe.