What did the Abbasid Dynasty do to help soften class lines between Arabs and non-Arabs?
The Abbassids allowed the Mawali (Non-Arab Muslims) to actively participate in governance and exempted them from taxation (like other Muslims). These changes from Umayyad policy paved the way for equality between Arab Muslims and Mawali.
To soften a plastic that has become hard, heat can be applied to gently soften the plastic. Softening clay like Play-Doh requires water. Softening acrylic paint will require water. Softening oil based paint will require paint thinner. To soften leather, water can be used and the leather stretched back into shape before it dries.