Answered by Shaykh Yusuf Weltch
Question
Are My Clothes Still Pure despite the Unclean Build-Up in the Laundry Machine?
Answer
In the Name of Allah, the Most Merciful and Compassionate
The unclean build-up, or in your words gunk, is not impure (najis). Impurities are very specific things determined by the Sacred Law as impure. Substances that are dirty/nasty, despite being such, are not impure.
That said, all of your clothes are considered pure, and any impure clothing put into the laundry cycle is considered purified by running the laundry machine. [Ibn ‘Abidin, Radd al-Muhtar]
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani