Alginate is a popular compound that is regularly used for life casting. When making alginate body molds, the artists have a choice of set times and even type of set of the mold to suit the application.
Alginate is the go-to material for making body molds for life casting. This is actually a dental impression material called sodium alginate that is derived from seaweed and forms a gel-like mixture when mixed with water. It is safe for the skin and also captures details very well, right down to the minutest creases on the skin and even the fingerprints.
The alginate that is used in life casting actually features a slower set time as compared to the dental formula. However, the regular set time of life-casting alginate can also prove to be short at times. It is always advisable to choose alginate with a sufficiently long working time to complete the job. And a little extra time is still better than not having enough.
In fact, alginate is formulated with varying set times to suit different applications. The traditional and regular formulae feature a set time of 4 to 5 minutes when mixed in the prescribed ratio of alginate powder to water.
Apart from this, there are special formulations with a slow set and fast set too – varying from 7 – 8 minutes to 3 – 4 minutes. The slow set allows a longer working window before the alginate will begin to set. On the other hand, the fast set formula comes in handy when working with children. It will set quickly and can be demolded soon without troubling the baby for long.
In addition to this, life casting artists play around with the set time by changing the thickness of the alginate mixture and the water temperature. The thicker the mix, the longer it will take to set and vice versa. Similarly, alginate that is mixed with warm water will set slower than alginate mixed in cool water. Testing with varying thickness and temperature will yield the ideal mix as needed.
Alginate set variation not limited to time
It’s not just about varying set times with different types of alginates, even the type of set can vary. Some formulas feature a softer set which is gentle on the skin, making them ideal for working with babies and small children. Regular alginates come with a firm set that is still bearable by adults. For a stronger mold, it is better to opt for fiber-reinforced alginate that not only comes with improved tear strength but can also hold moisture, thus delaying the shrinkage window by a considerable margin. This makes it suitable for large molds and full body castings.
Finally, the artist should also pay attention to the water being used to make the alginate mix. As a rule, hard water will make the mixture lumpy and unusable while soft water will give a smooth consistency to the alginate mix. Bottled water can be used when in a fix.
Happy Life Casting!