Using dishwashing liquid on a cast iron pan can potentially strip some of the seasoning, but if done sparingly and with care, it won't cause significant damage. Here are some tips on how to wash a cast iron pan with dishwashing liquid without completely stripping the seasoning:
Minimize dish soap usage: If you must use dishwashing liquid to clean your cast iron pan, use only a small amount. A little bit of soap can help remove stubborn residue without being too harsh on the seasoning.
Use a soft sponge or brush: Use a soft sponge or brush to gently scrub the pan's surface. Avoid using steel wool or abrasive scrubbers, as they are more likely to damage the seasoning.
Avoid soaking: Don't let the pan soak in soapy water for an extended period. Briefly clean the pan and rinse it immediately to minimize the contact with the soap.
Rinse thoroughly: After washing with soap, rinse the pan thoroughly under hot running water to remove any soap residue.
Dry immediately: Dry the cast iron pan immediately after rinsing. Water left on the surface can cause rusting, especially if the seasoning is partially stripped.
Re-season if necessary: If you notice that the seasoning has been significantly affected by using dish soap, you may need to re-season the pan. To do this, apply a thin layer of cooking oil to the pan's surface and heat it in the oven at a low temperature (about 375°F or 190°C) for about an hour.
Remember, washing cast iron with soap occasionally won't ruin it, but it's best to reserve this method for situations when you have stubborn residues that need to be removed. For regular maintenance, stick to using hot water and a brush or non-abrasive sponge to clean the pan. The natural oils from your cooking will help build and maintain the seasoning over time.
If you find yourself needing to use soap frequently to clean your cast iron pan, it might be a sign that you need to adjust your cooking techniques or revisit how you season your pan to improve its non-stick properties.