2012年考研英语二真题句子解析： Children were not colour-coded at all until the early 20th century: in the era before domestic washing machines all babies wore white as a practical matter, since the only way of getting clothes clean was to boil them.

Children were not colour-coded at all until the early 20th century: in the era before domestic washing machines all babies wore white as a practical matter, since the only way of getting clothes clean was to boil them.

冒号连接两个独立分句：第一分句"Children were not colour-coded at all until the early 20th century"有完整主谓结构，第二分句"in the era before domestic washing machines all babies wore white as a practical matter"同样有完整主谓（all babies wore white）。冒号在此起对等连接作用，第二分句解释说明第一分句的原因，两个分句地位对等，不存在主从关系。

colour-coded

"colour-coded"是过去分词作主语补足语，用于被动语态"were not colour-coded"中。从语义看，children与colour-code之间是被动关系（孩子被按颜色编码），过去分词表达这种被动含义。这里"colour-coded"补充说明主语children的状态。

in the era before domestic washing machines all babies wore white

主语"all babies"与谓语"wore"之间被长介词短语"in the era before domestic washing machines"分隔开。按正常语序，状语应置于句末或句首，此处状语前置并插在主谓之间，使主干"all babies wore white"难以直接定位，需要跨过中间的时间状语才能找到完整主谓结构。

to boil them

"to boil them"作不定式后置定语，修饰前面的名词"the only way"。从语义看，boil与way之间存在同位关系，不定式说明way的具体内容。这是"way to do sth"的典型用法，不定式充当定语说明方式方法。

were not colour-coded at all until the early 20th century

"not...until" 结构的核心逻辑是表达「直到某个时间点才发生某事」，其本质是通过否定 + 时间界限来强调动作发生的时间晚于预期或常规情况。

识别要点：主句必须包含否定词（not/never/no 等），"until" 引导时间状语（可以是时间点、时间从句或时间短语），两者共同表达「在 until 所指时间之前，主句动作未发生；到达该时间点时，动作才发生」。

本句中 "Children were not colour-coded at all until the early 20th century" 符合标准的 "not...until" 结构：主句 "Children were not colour-coded at all" 包含否定 "not"，"until the early 20th century" 是时间状语，整体表达「儿童直到 20 世纪初才开始按颜色区分穿着」。

翻译要点：不要逐字翻译成「不...直到...」，而应理解为时间的转折点，译为「直到...才...」。本句可译为：「直到 20 世纪初，儿童才开始按颜色区分穿着」。

迁移方法：遇到 "not...until" 时，先定位否定词和 until 引导的时间成分，然后理解为「在该时间点之前一直没有发生，到了该时间点才发生」，这样可以避免误读为简单的否定句。