Food and Beverage Tools
Muzaffat is that which is painted with tar, usually jars coated with tar where wine is kept. Soon the wine turns into wine because of the tar it is painted with. The reason for prohibition of keeping wine in these vessels is because it speeds up the intoxication process. So, perhaps someone may drink from it unknowingly.
Narrated Anas bin Malik, that the Prophet (PBUH) said, “Do not make Nabidh in Dabba (dry pumpkin) or tarnished jars”. Sahih Aljamei