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酯硬化酚醛树脂自硬砂的成功，是因为其造型性能好，以及烟雾和气味少。在本文中，利用各种再生技术研究了这种砂的再生性能。因为所用的树脂中含有氢氧化钾，这就引起在再生砂中有残余的钾。本文的研究表明，酯硬化酚醛树脂自硬砂的低再粘结性能，主要起因于含有无机和有机成分的可溶性混合物；其中也包括钾。提出一种新的热再生工艺，即在热再生前或再生后往砂中加入化学添加剂；这种已申请专利的化学添加剂能增加再生砂的活性，并改善其再粘结强度。
The success of esterified phenolic resins from hard sand is due to its good styling properties and its low smoke and odor. In this paper, the regenerative properties of this sand are studied using various regeneration techniques. Since the resin used contains potassium hydroxide, this results in residual potassium in the reclaimed sand. The study in this paper shows that the low re-bonding properties of the hardened sand of the ester-cured phenolic resin are mainly due to the soluble mixture containing inorganic and organic components; among others, potassium is also included. A new thermal regeneration process is proposed whereby chemical additives are added to the sand before or after thermal regeneration; this patented chemical additive increases the activity of the recycled sand and improves its rebond strength.