Why Use Softened Water
Water quality is one key factor in a successful dye reaction. Minerals dissolved in the tap and well water found in many regions can interfere with the dye reaction, preventing a substantial portion of the dye from bonding to the fiber. That is to say, so-called "hard" water can mess up the dye reaction - how badly depends on which specific minerals are dissolved in your water and their concentrations.
In many areas, water softener isn't needed at all because the water isn't "hard".
If nobody in your area sells water softener, it could mean that you don't need it. Some dyers skip the water softener and try a small test batch or two without it. However, the quality of a region's water can also change seasonally - so using softened water is an excellent measure to ensure that your dye reaction performs consistently throughout the year.
What is softened water?
Softened water falls into two categories - chemically softened and mechanically softened. Chemical water softeners "bind up" dissolved minerals so they can't interfere with the dye reaction, while mechanical water softening appliances actually REMOVE dissolved minerals from the water using reverse osmosis.
Sodium Hexametaphosphate is an economical and effective water softening agent commonly available through dye suppliers.
Avoid off the shelf water softeners which contain sodium carbonate (soda ash). DO NOT add any product containing sodium carbonate to dye premix solution, dye solutions or color dilution water (the bottle of "softened water"). Adding sodium carbonate to these solutions will cause the dye to react and exhaust before it can be used on fabric.
Do not use plain borax. While borax has certain "softening" properties, it also leads to the formation of peroxides which have a bleaching effect and are not desirable in the dye reaction system taught in the video series.
What's the difference between chemical softening and reverse osmosis?
The best thing about a reverse osmosis softener is that it actually removes much of the microscopic charged particles we call "hardness" from the water, rather than simply binding them in place in solution as chemical softeners do.
Chemically bound "hardness" particles still take up "space" in the water where something else could otherwise be dissolved. And when you dissolve a chemical softener such as Sodium Hex - that's one more thing the water has to hold in solution in addition to all those dissolve minerals we call hardness. This means that chemically softened water has less "space" available to dissolve urea and dye than an equivalent volume of reverse osmosis softened water.
Using water treated through a reverse osmosis softening appliance sets the ideal conditions for the dye reaction and leads to substantially brighter and longer lasting colors. Not only will your tie-dye come out better - a water softening appliance will also make your water heater and pipes last longer, and your household laundry and dishes will come out cleaner using less detergents.
Do I really need a softening appliance?
Sodium Hexametaphosphate will work just fine, but a softening appliance does have benefits.
If you do a substantial amount of dyeing, a reverse osmosis water softener is a worthwhile investment. Installation is relatively simple, but you do need a handyman or plumber who can splice it into your cold water line at the right spot. Then all you do is plug it in, program it (it's like setting a digital watch, but not as tricky as a VCR) and add inexpensive coarse softener salt once in a while.
One thing you have to watch out for is running the water in the house when the softener appliance is recharging. Almost every softener out there goes into "bypass" when it's regenerating, because it has to run backwards to regenerate. This means when it's regenerating, the water coming in to the house bypasses the softener and is regular old "hard" water. What happens is, say you take a nice long shower while the softener is recharging and as the water heater empties, it refills with "hard" water.
Then the softener gets done recharging, and you start mixing dyes and using hot water, but the hot water you're using is "hard" water that found it's way into the water heater while the softening appliance was in bypass. Oops, I've let that happen more than once.
If you're on a well rather than a municipal water system, you should also consider whether the water softener is before or after the storage tank (if you have one). A storage tank can end up full of "hard" water just like a water heater.
If you prefer something in between
There are also small "under the sink" softening units available which will work for one faucet rather than a whole house - these are somewhat less expensive, easier to install and portable. While we like the big "whole house" units because they soften the water to the washing machine and water heater, they simply aren't an option in every situation.
That's where a portable unit comes in handy, so at least you can get that precious softened water from one faucet.
When using a portable water softener, simply pre-rinse your fabric in softened water and let it drain with a strainer before folding (rather than the regular machine pre-wash). That way the fabric doesn't become contaminated prior to dyeing with minerals from the unsoftened water in the washing machine.
Learn more about making tie dye here.