关于底皂青焐灰的探讨——陈缶文

"焐灰"这一术语，源自古代陶瓷工艺，意指将未经完全烧制或需改色茶壶置于陶瓷钵内，用柴草灰进行密闭低温缺氧烧制，以利用紫砂主要着色的铁离子在低价状态下形成深黑色。紫砂壶经过此过程，被赞誉为“温润如墨玉，坚质似铁石”。然而，由于目前掌握此技艺的工匠稀少且容易出错，使得仿焐灰泥料成为了市场上的替代品，不免给紫砂行业带来了不公正的评价。

实际上，“焐灰”就是一种还原烤漆技术，其着色离子仍是铁离子，但主要是高价铁离子，在缺氧环境下还原成低价铁。因此，它对人体无害。

与添加颜料后的茶壶相比，质感差异明显，而颜色可能接近但质感平滑、颗粒感淡薄。此前，“焐灰”是一种补救老茶壶欠火（俗称生壶）的方法，因为其效果尤为显著，如同“墨玉一般”，在市场上拥有特殊地位，有些收藏家甚至专门购买第二次烧制过的已有作品进行再次焐化处理（价格也会翻倍）。

有一位网友询问，一本书中提到紫砂通过碳渗透来实现颜色的变换。我不知该作者身份，但我清楚的是，“焐灰”的核心就在于在还原气氛中使高价铁离子回归红色，然后在缺氧状态下转变为黑色的低价状态。如果真实存在碳渗透，那么使用后是否会出现碳析现象？

理论上，只要是以铁离子作为着色剂，在缺氧条件下都可施行。但具体操作复杂，对火候要求严格，朱泥类易结晶度较高，因此液相相对温度偏低。因此成功率极小。而对于底皂青矿物，因掺入了更多调配，可以调整花纹和顏色，但也有可能导致花壶现象发生。

“Flawless Flushing of Ferrous Oxide: The Art of Purple Clay Tea Pots”

Purple clay tea pots have long been prized for their unique beauty and durability, with the process of "flawless flushing" being a closely guarded secret. This ancient technique involves sealing the pot in a ceramic container and using charcoal to create an environment that is both low-oxygen and high-temperature.

The result is a color that is described as "warm like ink jade, solid like iron stone." But as the number of skilled artisans decreases, so does the quality of the final product. To combat this, some manufacturers use chemical additives to mimic the effects of flawless flushing.

But what exactly is flawless flushing? It's simply a matter of reducing oxidation by creating an environment where ferrous oxides are allowed to convert into ferric oxides. This process not only enhances the color but also improves durability.

While other methods may produce similar colors, they lack the texture and depth that comes from genuine flawless flushing. And as one collector noted, "the more you use it, the better it gets."

So why do collectors pay such a premium for purple clay tea pots? Because they know that each one has been carefully crafted through years of experience and tradition.