Engineer's Blue: Prussian Blue Ground into a Marking Paste

Engineer's blue is a heavily pigmented paste that shows where two surfaces touch: smear it thinly on a true flat, rub the work on it, and the blue comes off only on the high spots, which are then scraped down. Joseph Whitworth made accurate flat surfaces this way in the 1830s. It is Prussian blue ground into a grease. The picture: how the blue marks the high spots (our drawing).

初学者

Half an hour

说明

Soften the grease

Warm the tallow just until it softens.

此步骤所需材料：

牛脂60 克

所需工具：

等臂天平

电热板

Grind in the pigment

Put Prussian blue on a glass slab, add the soft grease a little at a time and grind it with a muller until the paste is smooth and deep blue, with no grit: about one part pigment to three of grease (our proportion).

此步骤所需材料：

普鲁士蓝20 克

所需工具：

玻璃板

玻璃研磨器

调色刀套装

橡胶手套

Tin it and test

Scrape it into a small tin with a lid. Test it: smear a film thin enough to be translucent on a flat plate, rub a part on it, and only the touching spots should pick up blue.

所需工具：