Soy wax differs from other candle waxes in its unique chemical structure. Compared to paraffin wax, soy wax is environmentally friendly, renewable, and biodegradable. This article focuses on the science behind soy wax melting points, detailing the exact temperature ranges of the different types of soy waxes and offering precise measurement techniques to achieve perfect results each time.
Proper temperature control is important for successful soy wax candle-making as soy wax destabilises when heated above 180°F. The result:
Under-heating (below 170°F) can be equally undesirable due to incomplete melting, affecting your candle quality.
The reaction of soy wax candles to heat is better understood by taking a closer look at their composition.
Soy wax is produced from hydrogenated soybean oil, a vegetable oil from soybeans. Hydrogenation is adding hydrogen atoms to soybean oil to transform it into a solid state. This provides a wax with a lower melting point and a smoother, creamier texture, with the added benefit of being ecologically friendly.
Chemical Composition of Soy Wax
Soy wax has a density of 0.9 g/ml, which is about 90% of the density of water and is lighter than most waxes. It is composed of:
Hydrogenation completely changes the melting characteristics of soybean oil. Manufacturers use a nickel catalyst to add hydrogen to oil molecules at high temperatures (140-225°C). The process converts unsaturated fatty acids to saturated fatty acids, which makes the oil thicker and thus raises its melting point.
The level of hydrogenation dictates the melting point of soy wax. Partially hydrogenated soft soy waxes have lower melting points (~20°C onset, 39.0°C peak), while fully hydrogenated hard soy waxes have much higher melting points with peaks at 52.8°C and 63.0°C. Fully hydrogenated soybean oil can even reach melting points as high as 65.48°C, which is suitable for heat-resistant applications.
One of the defining characteristics of soy wax is a complex crystalline structure composed of a mixture of hydrocarbon chains. It's this unique structure that enables soy wax candles to burn longer as well as to release fragrance at a lower temperature.
Soy wax crystals (frosting) are the natural result of soy wax being mixed with oils, a phenomenon that is increased by temperature fluctuations. Soy wax will normally crystallise between 44.7-47°C. The way it crystallises will influence the appearance and texture of the resulting candle. Pure soy wax will take about two weeks to cure after it has been made stable. The waiting period allows the crystalline structure to form completely and bind with any fragrance oils.
Environmental conditions during hardening determine the final crystal structure. Faster cooling creates more small crystals, and slower cooling creates larger, more discrete crystalline structures that change the candle's appearance and its burn time.
Soy wax comes in many different formulations, each with its own melting characteristics. Lab tests show that the melting points differ with the various types of soy wax and their uses. Let us look at the temperature ranges for different blends of soy wax.
Pure soy wax melts between 120°F and 140°F (49-60°C). Its soft melting point makes it suitable for container candles, where containers help maintain shape. Natural 100% soy blends all reach their highest melting point at around 52°C. Golden Brands 415, to name just one, melts at precisely 121°F (49.4°C).
Pure soy wax needs slow cooling to minimise frosting. The wax achieves full melting at lower temperatures than paraffin varieties and freezes at around 34°C.
Container blends offer crafters greater temperature versatility. The blends melt, on average, at 124°F, but individual formulations may differ. Commercial container waxes melt between 115°F and 135°F, with some melting as high as 145°F.
There are some excellent container waxes available on the market. Golden Brands 464 works best at a 135°F (±5°) pouring temperature. SB 1000 soy blend melts at 130°F. Midwest container wax melts at 125°F.
Pillar blends need higher melt points to hold their form without the support of a container. These special formulations range from 130°F to 200°F. Blended Waxes Pillar Soy (BW-921) is 135°F (57.2°C), while the EcoSoya Pillar is slightly lower at 131°F (55.0°C).
The use of additives in pillar blends raises their melting points above those of standard container waxes. Low-melt pillar blends start at around 130°F, while high-melt ones reach up to 150°F. These high temperatures enable the candles to maintain their shape.
Experts recommend not heating soy wax above 200°F because it tends to turn yellow. Most manufacturers suggest heating to 170-185°F before adding fragrance.
The melting point of soy wax varies. It is affected by some key factors. Awareness of these variables enables candle-makers to anticipate and control their wax's behaviour.
The melting point of the wax is determined by the quality and source of the soybean oil. Soybeans with a higher content of unsaturated fatty acids will yield wax with a lower melting point. Researchers have developed soybeans containing just 7% saturated fatty acids, which changes their thermal properties. The iodine value (IV) of soy wax indicates unsaturation levels and drops from 49.7 to 45 as palm stearin increases from 60% to 70%. This shows the influence of oil composition on melting behaviour.
Hydrogenation is the main process that affects soy wax melting temperature. The chemical modification changes unsaturated fatty acids to saturated forms and raises the melting point. The cooling rate during production also has an effect. Quick cooling creates smaller crystals, while slow cooling creates larger crystalline structures. The internal crystal size affects candle burn and fragrance throw. Larger crystals can cause the fragrance to settle at the bottom of the candle.
Apart from composition, environmental conditions affect the melting behaviour. Atmospheric pressure, room temperature, and humidity can modify the melting point when testing. Candles can soften in tropical climates with high humidity, even with air conditioning. Test results also vary with the equipment used. DSC (Differential Scanning Calorimetry) and standard softening point methods have temperature variations of about 5.2°C.
To determine the precise soy wax melting point, you would need specialised equipment and techniques. Your setting - home studio or professional lab - dictates the method. Each of the procedures below gives you different levels of precision to determine the temperature at which soy wax melts.
Professional labs use standard ASTM methods to ensure reproducible results. DSC analysis measures the heat needed to raise the wax temperature and provides precise melting point data. This method detects subtle phase changes that can slip by with rudimentary equipment. The Congealing Point of Petrolatums and Waxes test identifies when liquid wax develops a solid crystalline structure. At least three separate measurements are needed in laboratory testing to achieve consistent results.
The amateur candlemaker can handle less complex operations. You'll need a heat-proof container, a heat source with precise control (a double boiler), and a reliable thermometer. Note and record the temperature as wax melts from solid to liquid. Some candle-makers find more stable results by reading cooling curves instead of heating curves. Room temperature has a profound influence on your results, so keep it at a constant 70°F or so during tests.
Digital probe thermometers give you greater accuracy with soy wax temperature readings. They register the actual inner temperature, while infrared thermometers register surface temperatures. Most digital thermometers work perfectly in the -58°F to 572°F range, which covers all soy wax needs. Stirring when you're using digital thermometers is advisable since the wax temperature rises a little during the process. Infrared thermometers might seem convenient since they're non-contact, but room temperature and shiny surfaces tend to interfere with their accuracy.
Temperature readings need context. Wax starts melting around 120°F but isn't fully liquid until 130-140°F. The optimal melting temperature is 170-180°F, however, fragrance performs best at 185°F. Wax starts crystallising at 44.7-47°C during cooling. Temperature readings may vary by around 5.2°C based on equipment calibration.
Soy wax melt points are the secret to successful candle making. This article has shown that soy wax's unique melting properties are due to its chemical structure and processing.
Pure soy wax starts melting at 120°F, while special pillar blends can handle 200°F. Many different factors create these variations. The quality of the soybean oil, the degree of hydrogenation, and environmental conditions all play a significant role. The manufacturing process affects crystal formation and the final product quality, especially if the cooling rate changes.
Obtaining the correct temperature is one key aspect of reproducible results. DSC testing in the lab provides accurate readings. Home candle makers can achieve consistent results through the use of digital probe thermometers and good test procedures.
This information can help candle-makers choose the right types of wax, maintain optimum processing temperatures, and troubleshoot common problems. Temperature ranges and accurate measurement methods are a great way of getting better results. With these facts at hand, it is far easier to create high-quality soy candles.
