Making and pouring isomalt can be a tricky, sticky business. These handy tips are from Chef Dominic Palazzolo of Make Your Own Mold:
Use distilled water. Many parts of the country have what is called “hard water.” The minerals in tap water can turn brown when exposed to elevated temperatures, but because there are so little of these minerals, you will end up perceiving it as a yellowing effect.
Add only enough water so the isomalt looks like wet sand.
Use stainless steel pots and stainless steel utensils for stirring. Do not use a wooden spoon. Foreign materials in the wood leach out into the isomalt which can turn the mixture yellow.
Do not use a natural bristle brush to wash down the sides of the pot once isomalt comes to a boil. Use a nylon pastry brush. There are a host of chemicals and conditioning agents in the natural bristles that can turn your isomalt yellow.
Stop stirring the isomalt water mixture when it comes to a boil.
Test your candy thermometer, as many of them read inaccurately. Test by bringing water to a boil and inserting thermometer. Observe the temperature it shows. It should read 212° F.
Cook isomalt to 338° F. Take off heat at about 334° and place bottom of pot in water to stop the cooking process. Allow the pot to stay in water only until the hissing stops. This should take about 5 seconds.
Place isomalt in a 265° F oven and allow to cool for 15 minutes. You will have no bubbles and pure, clear liquid crystal to pour all day.