The Hay Slow Cooker (hooikist) was invented in the Netherlands around 1900 and especially popular during the Second World War, when heating fuel was scarce. Nowadays it is forgotten, which is a pity as it can save up to 80% on cooking fuel costs. The Hay Slow Cooker is ideal in temperate climates for long cooking food in liquid such as beans, pulses, rice, grains, stews with meat like goulash, chicken pots like coq-au-vin, potatoes, porridge, soup, etc.. In warm climates a solar cooker is probably more practical. Do not slow cook fresh vegetables, steaming is the best way to preserve vitamins. The Hay Slow Cooker is easy and cheap to make and your food will never burn! It is also said that the Hay Slow Cooker is perfect for cooking large quantities, as the heat is spread more equally than on a stove.
How it works
A pot on the stove requires continuous heating because it is constantly losing heat to its surroundings. A Hay Slow Cooker wraps around a hot pot and insulates, thus keeping the heat inside much longer. Only 20% of the normal cooking time on the stove is needed, the hay will do the rest of the cooking for free.
How to use the Hay Slow Cooker
Boil the food on the stove one fifth (1/5) of the normally required cooking time up to a maximum of 20 minutes. Transfer the pot quickly to the Hay Slow Cooker. Leave the pot 3 times the normally required cooking time in the Hay Slow Cooker. Foods that require a very long cooking time can be reheated shortly to boiling point on the stove and then returned to the Hay Slow Cooker to continue cooking. Reheat the food to boiling point before serving to be sure of food safety.
Filled almost to the brim with 4 liters (1 gallon) of boiling water and beans, the fully cooked contents of the pot were still 70 degrees Celcius / 158 degrees Fahrenheit after staying for 6 hours in the hay slow cooker of this instructible. These figures will vary depending on the size and model of the pot and hay slow cooker.
Step 1: Tools and Materials
To start, you need a large cooking pot with a well fitting lid. The hay and fleece cover will be custom made to fit this particular pot. Preferably the knob on the lid and the handles should protrude as little as possible. A long handle as on a sauce pan is not suitable.
� cotton fabric ( a few old shirts, a bed sheet)
� fleece (from old sweaters)
� cord or ribbon, about as thick as shoe laces
� newspaper or other paper for templates
� hay (dried grass, I used a 1 kg pack of rabbit fodder, 1.20 Euro / 1.60$ at the local supermarket). Straw, which is thicker than hay, is less suitable because it insulates less well.
Sewing machine, sewing needle, thread, scissors, safety pin or special needle to thread the ribbon/cord, pins, measuring tape
Only beginners sewing skills are needed. Except for the circumference of the small circle for the rectangle, the measurements need not be very precise. A few centimetres (around 1 inch) more or less do not matter: just fill the pillows with more or less hay for a good fit around the pot.
Step 2: Measurements & Templates
Measure the following:
� the diameter of the pot
� the height of the pot up to the knob of the lid
Cut the following templates out of newspaper :
� a small circle with a diameter equalling the diameter of the pot + 14 cm (5.5 in)+ 2 x 1,5 cm ( 2x 0.6 in) seem allowance. The handles of the pot should fit within this circle.
� a large circle with a diameter equalling that of the smaller circle including seem + 30 cm (12 in)
� make a copy of the small circle. Fold it in half. Ad 2.5 cm (1 in) to one half, and cut on this line. Use the larger part, discard the other part.
� 1 rectangle
length: circumference of the small circle (= 3.14 x the diameter excl. seems of the small circle) + 3cm (1.2 in) seem allowance
width: height of the pot + half of the diameter of the small circle + 10 cm (4 in) extra + 3cm (1.2 in) seem allowance
� 1 long rectangle
length: circumference of the small circle (= 3.14 x the diameter excl. seems of the small circle) + 20 cm (8 in) extra + 3cm (1.2 in) seem allowance
width: height of the pot x 2 + 10 cm (4 in) extra + 3cm (1.2 in) seem allowance
Step 3: Cut the Fabric Pieces
Use the newspaper templates to cut the following:
3 small circles
2 large circles
4 slightly- larger than-halves of the small circle
1 rectangle (this will form the sides of the slow cooker. If you do not wish some fleece to be visible on the inside, double the width of this rectangle)
1 long rectangle
4 small circles
1 large circle
Cut 1 piece as long as the circumference of the small circle (3.14 x the diameter) + 20 cm (8 in) and 1 piece as long as the circumference of the large circle (3.14 x the diameter)
Step 4: 5 Finished Parts
Before starting to sew step-by-step, first an overview of the finished project.The finished Hay Slow Cooker will consist of 5 separate parts that fit easily together without buttons, knots or Velcro:
� 1 top bonnet (the large circle) with a pocket (2 half circles) for a round pillow (small circle)
� 1 bottom bag (small circle and rectangle) with a pocket (2 half circles) for a round pillow (small circle)
� 2 round pillows (small circles) filled with hay
� 1 circular tube pillow filled with hay (long rectangle)
Step 5: 2 Round Pillows Filled With Hay
� place 1 fleece small circle and 1 cotton small circle on top op each other, right side inside
� sew the outline of the 2 circles together leaving an opening large enough for a fist filled with hay
� turn the inside out
� zigzag the sides of the opening separately
� repeat for second pillow
� iron the seems
� Fill the pillows with loose hay, but do not yet close the opening
Step 6: 2 Pockets for the Round Pillows
� seem the straight side of the 4 cotton halves. The finished halves should overlap +/- 1 cm (0.4 inch) when forming a circle
� place 2 cotton halves on 1 fleece small circle, right side inside. The finished halves should overlap +/- 1 cm (0.4 inch)
� sew the outside of the circle together
� Repeat for the 2nd pocket
� Turn the 2 pockets inside out, right side is now visible. Iron the outside seems.
Step 7: Top Bonnet
� Place a small circle pocket in the center of 1 large cotton circle. The fleece side of the small circle pocket touches the right side of the large cotton circle.
� Pin the pocket to the large cotton circle, and sew the outside of the small circle pocket , to the large circle, as close to the edge of the pocket as possible.
� Flatten the large fleece circle on the table. Cover it with the other large cotton circle without pocket, the right side up. Cover with the large cotton circle with pocket, wrong side up, pocket invisible.
� Pin and sew the 3 large circles together on the edge. Leave around 15 cm (6 in) open to turn it inside out.
� Turn the inside out. Both sides are now the right cotton side. One side has the pocket with a slit in the middle, the other side is smooth. Iron the seems, fold the seems of the opening to the inside.
� Close the opening neatly, leave a gap of 1 cm (0.4 in) for the ribbon/cord.
� Stich the edge of the circle, at 2 cm (0.8) of the edge. This forms a tunnel through which the ribbon can be threaded.
� Thread the longest ribbon through the tunnel. Knot or sew the ends together.
� Insert a still open round pillow filled with hay in the pocket.
Step 8: Bottom Bag
� Place the fleece rectangle and the cotton rectangle on each other, right sides inside. Pin and sew one long side together, stop 2,5 cm (1 in) from the edge.
� Fold and iron the four open corners at the end of the seem to the wrong side of the fabric. These will make an opening for the ribbon. Stitch along the corner fold.
� Fold the fleece and cotton piece in half, the right side on the inside, fleece on fleece and cotton on cotton. Pin and sew the short sides of the rectangles together. There will be a small gap in the middle of the seem for the ribbon.
� Reverse and fold along the long seem, so that the tube has now 1 right cotton side and 1 right fleece side on the outside. Iron the seem. Pin and sew along the long seem (attaching fleece and cotton together), 2 cm (0.8 in) from the edge. This forms a tunnel through which the ribbon can be threaded.
� Thread the shortest ribbon through the tunnel. Knot or sew the ends together.
� Pin and stitch the small cotton circle to the tube, thus creating a cylindrical bag open on one side. The wrong side of the seems is on the fleece inside (solid red on the photo) of the bag.
� Pin and stitch the circle pocket to the inside bottom of the cylindrical bag. All the seems are now hidden. The slit of the bottom pocket is accessible. Stitch as close to the edge as possible.
� Insert a round pillow filled with hay and not yet closed in the bottom pocket of the bag.
Step 9: Inner Tube Pillow
� Pin and sew the long side of the long cotton rectangle together, thus creating a long tube
� Fill the tube loosely with hay, from both sides. Fill it evenly, without bumps or bulges.
� Insert one end of the tube into the other, as if it were an arm inserted into a sleeve.
� Use a few pins to keep the ends of the tube together.
� Place the round tube inside the cylindrical bag
Step 10: Final Fitting
� Put the empty pot in the bag. Observe how it fits. If the pot is hugged too tightly, remove a little bit of the hay from the side pillow. If you can see space between the side pillow and the pot, add some hay to the side pillow. The bottom pillow should not be filled so round as to make the pot wobble. The side pillow should gently touch as much of the side of the pot as possible.
� Close the bag with the ribbon.
� Place the top bonnet on the bag and tighten the ribbon. The pillow in the bonnet should not be so round as to create gaps on the side of the top. If the lid of the pot has a protruding knob, try to "dig" a hole with your fingers in the hay of the top pillow where it can fit.
Step 11: Close the Pillows
� Close the two round pillows by hand. Use a few large stiches, easy to cut if you want to empty the pillow for washing or if you want to add or renew the hay. Dont worry about making it a nice seem, it is completely invisible when inserted in the pocket. Alternatively you could use 2 or 3 safety pins.
� Close the tube pillow by hand. This seem will be visible, so try to make it neat looking. As there is no stress on this seem, and as the hay does not spill easily out of the pillow, you can use a few large stiches. Alternatively you could use 4 or 5 safety pins, and cover them up with a nice broad ribbon.
Step 12: Food Safety
At 63 degrees C (145 F) or more, many spoilage bacteria are killed, as Louis Pasteur discovered when he developed the industrial process of pasteurization.
Many yeasts and bacteria will grow optimally at a temperature of 30-37 C (86-98 F). My guess therefore is that it is best to avoid keeping food in the Hay Slow Cooker long enough for the food temperature to drop below 63 C (145 F).
To be extra sure, it is best to reheat the food shortly (2 minutes) to 74 C/ 165 F or to boiling point before serving.
Rice should be treated extra carefully. Uncooked rice can contain spores of the food poisoning causing Bacillus cereus that can survive even boiling temperatures. So try not to activate those spores in rice by avoiding keeping it at temperatures between 5C and 63C (41F and 145F).
Step 13: Trial and Mods
The traditional Dutch Hay Slow Cooker is a wooden chest lined with cotton bags filled with hay. Both wood and hay are insulating. Anything that keeps a person or a home warm can work as a pot insulation: hay, a blanket, a sleeping bag, crumpled newspaper, crumpled tissue paper, corrugated cardboard, wool, rags, a cooler, etc.
If you want to try first before making one yourself, wrap your hot pot in a blanket or sleeping bag and see how it works.
Requirements for your own design
The pot or pots should fit inside the Hay Slow Cooker so as to touch the wadding loosely from all sides. The wadding should be soft and loose like a pillow, not packed or stretched tightly.
2. Heat resistant inside
Before making the version of the Hay Slow Cooker described here, I sat a hot pot of pink beans overnight on a bean bag filled with polystyrene pearls, and wrapped it in unlined synthetic wadding used for clothing. The pink beans were great, soft enough for a toothless baby. However, the polystyrene pearls in the bean bag had slightly clotted, and the synthetic wadding at the bottom of the pot had melted into clumps. This taught me that the materials touching the pot, and especially the bottom which is hottest, should be heat-resistant. So be careful before spoiling your favourite sleeping bag in a trial! Natural materials, such as cotton or linen fabric, and hay or wool wadding work best for the inside.
3. Avoid spilling
A hot pot filled with liquid is not the easiest thing to wrap in a blanket or place in a small box without spilling. In my first trial, I spilled some liquid as I was wrestling with the heavy pot and the synthetic wadding. A wet spot will act as a heat conductor instead of insulating. Whatever design you develop for a slow cooker, try to make placing the pot in it as easy as possible, in order to avoid heat loss due to spillage.
4. The outside
The outside container of the wadding could be synthetic such as a plastic cooler, or a cardboard box lined with polystyrene plates. The outside could be rigid or soft, as long as it helps insulating.
Step 14: Servings and Maintenance
Slow cooking is especially useful for large quantities of food. The larger and fuller the pot, the slower it will cool down. That works well with beans and pulses. I cook them in large quantities that I divide and freeze into 1 person servings. I find however that freshly cooked rice tastes better than rice that has been frozen. So I prepare rice in a small pot suitable for 1 meal and place it in the large Hay Slow Cooker pot filled with boiling water.
As the hay (or paper or wool) wadding compresses over time, the Hay Slow Cooker will lose some of its insulation capacity. Renew the wadding once in a while to keep optimal performance.