Illustrated by Peter Strain

Zakariya Al-Razi, the Secret of Secrets, and the invention of the modern still

Distillation is a purification technique that every chemist knows well. Since different chemical compounds boil at different temperatures, chemists can separate one desired substance from another through selective heating. We use distilling equipment to make everything from distilled water to ethanol to gasoline.

Book cover image of William Gurstelle's ReMaking History Volume 1

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Although distillation has been around since ancient times, the modern process traces its roots to medieval Islamic alchemists. Zakariya Al-Razi was foremost among them. A tenth-century Persian alchemist, physician, and philosopher, Razi is considered by many historians to have devised and put forward in writing the foundations of modern chemical distillation.

In his manuscript with the rather thrilling name The Book of the Secret of Secrets, Razi (also known as Rhazes or Rasis in the West) lays out the equipment, chemicals, and techniques involved in efficiently distilling a great variety of substances including kerosene, alcohol, and essential plant oils. While others wrote about distillation before him, it is Razi who first describes using the three main components of modern distilling equipment: the qar’a (boiler), the anbiq or alembic (distillation head) and the qabila
(the liquid receiver.)

In this issue’s Remaking History project, you’ll follow in Razi’s footsteps during the Islamic golden age and fabricate a working copper alembic pot still, capable of distilling many substances. With this equipment, you can make purified water, essential oils such as rose water and lavender oil, and even ethanol (alcohol) — which Razi also discovered!

1. CUT OUT THE PIECES

Use the ruler, metal scribe, and flat dividers to lay out cutting lines on the copper sheet for all the rectangular pieces, as shown in the cutting diagram. Don gloves and use the aviation snips to cut the pieces. Sand all the edges smooth.

download the diagram in PDF by clicking here

Use the protractor, ruler, dividers, and scribe to lay out the boiler cape shown in the cutting diagram and below. Use the snips to cut the boiler cape. Sand the edges smooth.

Caution: Sheet metal work and soldering require goggles for eyes and gloves for hands. Burns and cuts may occur if proper safety measures are not followed. 

In similar fashion, lay out the alembic cape as shown in the cutting diagram. Cut out and sand the edges.

2. MAKE THE BOILER

Using the cardboard tube as a form, bend the 8″×24″ sheet into a cylinder. Remove the tube, overlap the ends by ½”, and use the clamps to hold the copper sheet while you do the next two steps.

Starting ½” from the bottom, drill 3/16″ holes every 1″ along the copper sheet, 3/16″ in from the edge.

Insert the #8 machine screws into the holes. Tighten the nuts on the inside, and then remove the holding clamps.

Flux the overlapping seam. Use the propane torch to heat the metal and when sufficiently hot, solder the joint. For a demonstration of how to solder a copper boiler, check out this video.

Center the copper cylinder on the 8″ copper square. Trace the cylinder outline onto the square. Measure and mark another circle 1/8″ inboard from the outline. Use the snips to cut out the circle of the outlined cylinder (cut on the outer line, not the inner line).

Starting from the scribed inner line, use the vise-grip pliers to bend a solder lip into the copper. It’s best to do this in two passes so as not over stress the copper as you bend.

Insert the bottom into the cylinder. Use the pliers to adjust the solder lip on the bottom so it fits into the cylinder without gaps.

Flux the seam and solder, again using the pliers to close any gaps.

Carefully bend the boiler cape into the shape as shown, with the edges overlapping by ½”.

It may take some gentle prodding to make the cape completely round. When you’re satisfied with the shape, use the vise-grips to hold the cape in place while you complete the next step.

Drill three 3/16″ holes in the boiler cape, 3/16″ in from the edge. Insert #8 machine screws and nuts. Flux the seam and solder.

Place the cape on the boiler cylinder wall. Mark a 1/8″ overhang from the boiler wall on the cape and use the tin snips to cut and remove the excess. Use the vise-grips to bend a solder lip parallel to the boiler wall.

Place the boiler cape over the cylinder wall. Use a hammer to gently tap the copper so there are no large gaps between the cape and the boiler wall. Flux and solder the wall and boiler cape together.

Carefully bend a ½”×14″ inch strip into a ring that fits atop the upper opening of the boiler cape. Allow for a ½” overlap and cut off the remainder. Flux and solder the ring.

Place the ring atop the upper opening of the boiler cape. Flux and solder the ring to the cape as shown.

3. MAKE THE ALEMBIC

The alembic detaches from the boiler to facilitate cleaning the inside of the still. The two pieces connect via two close-fitting rings, one inside the other. One ring you’ve already soldered to the boiler; the other you’ll solder to the alembic. Then the rings simply slide over each other; this joint is not soldered.

Bend the alembic cape into a truncated cone and overlap the edges by ½”. The top opening should measure 11/8″. If not, readjust the cone. It may take some gentle prodding to make the cape round and symmetrical.

NOTE: if necessary, you can use the snips to cut the opening to 1½”.

Use the vise-grips to hold the cape in place while you drill two 3/16″ holes, 3/16″ in from the edge and ½” from the top and bottom edges. Fasten with the remaining #8 machine screws and nuts. Solder the seam.

Carefully bend the other ½”×14″ strip into a ring that fits snugly inside the ring on the boiler cape. Allow for a ½” overlap and cut off the remainder and solder the ring.

Place the alembic cape atop the ring and mark the circumference with a marker. Use the vise-grips to bend a solder lip; you may find that cutting a few slits at intervals makes it easier to bend.

Use the vise-grips to press out any large gaps, then solder the ring to the alembic cape. The image below shows the finished alembic and boiler.

4. ADD A CONDENSER COIL

Drill a ¼” hole through a #7-sized silicone stopper. Insert one end of the ¼” soft copper tubing through the hole and bend the rest of the tubing into a gentle spiral.

Insert the stopper into the mouth of the alembic. If necessary, use the vise-grips and a file to shape the alembic opening so the stopper fits snugly.

5. TEST FOR LEAKS

Fill the still with water and test for leaks. Fix any leaks by resoldering, or use high-temperature sealant.

Congratulations! Your still is complete.

USE IT

Your pot still has a capacity of a bit more than 1 gallon, which is perfect for many small distillation projects. It’s suitable for making ultra-pure water, essential oils such as rose oil and lavender essence, and small batches of ethanol fuel. Depending on what you choose to distill, you may need to place the copper condensing coil inside a bucket of cold water in order to condense the distillate properly.

CAUTION: plumbing solder melts at obove 400F. Use an electric hotplate, not open flames. Never heat the still without liquid inside, as the solder joints may melt. 

There are many excellent books that provide instructions on how to use a still like this to produce essential oils, purified water, or alcohol. Read and follow those instructions, mind your local laws, and
enjoy using the stuff you make.

William Gurstelle’s new book series Remaking History, based on this magazine column, is available in the Maker Shed.