Lady Dye offers a hot water range and a cold water range of dyes...
Because Lady Dye dyes are used in the home, they're formulated for use on natural fabrics†.
Furthermore, because they're designed for use in Southern African conditions, they're formulated primarily for use on cotton and cotton-derived fabrics such as linens, denim and cotton viscose.
- The hot water range, consisting of 46 shades, require a very hot holding temperature to achieve the desired shade (100°C)
- The cold water range, consisting of 28 shades, require a cooler holding temperature - around 60°C - though perhaps it would be more realistic to think of them as warm water dyes.
Hot or cold - which one should I use?
From a usage point of view, hot water and cold water dyes compare favourably in terms of efficacy and performance. A certain school of thought has historically held that hot water dyes are stronger and brighter, but cold water dyes do not need to be applied cold as a matter of rule, and they perform extremely well at somewhat raised temperatures.
On the other hand, cold water dyes have to be used for batik - a dyeing process involving masking selected parts of the fabric with wax - because of its greater effectiveness at lower temperatures. Furthermore, cold water dyes can be used for microwave dyeing, whilst hot water dyes can not. Cold water dyes are favoured for use in remote areas, where the availability or costs of domestic power are important considerations.
Both dye types can be used in washing machine dyeing, and both can also be used to tie-dye, a technique where areas of the fabric are prevented from being dyed by being tied up tightly in various patterns.
At the end of the day, which dye type to use is a matter of personal preference, and unless you want to use a microwave oven to dye or do a batik technique (both of which will require you to use a cold water dye), it doesn't really matter which one you choose.
† synthetic fabrics such as polyester and polyacrylics can only be dyed in an industrial environment, involving high temperatures and high pressure