Save money while you avoid the synthetic fragrances and other additives in commercial laundry detergents by learning how to make a DIY laundry detergent at home.
Begin by adding the surfactants to your container. I cleaned out an old laundry detergent bottle from a natural laundry detergent that I had bought in the local eco-supermarket. The easiest way to add them is to tare the scale with your container on top to set the scale to zero. You can then add one of the surfactants before taring the scale again. Taring the scale between adding each ingredient is the easiest way to weigh out your ingredients.
Once you've added the surfactants, add the distilled water. You can now gently stir or agitate the bottle to mix the surfactants with the water. Mix them gently so as not to form too much foam.
You can now add the salt into your mixture, again gently stirring to incorporate it. The mixture will thicken up as the salt dissolves into the mixture. (You can also choose to separate out a small portion of the water and dissolve the salt in that water before adding it to the detergent mixture. This may help more efficiently combining all ingredients more easily.)
Finally, add your preservative. I like to switch to a smaller, more precise scale for weighing out my preservative and other ingredients used in smaller quantities. (This scale is a good example.)
You are now ready to use your homemade detergent just as you would a store bought one. (I'd suggest using around 2-3 Tbsp. per load.) To help boost cleasning, you could consider adding some baking soda to your wash water too and/or use vinegar in your final rinse as a natural fabric softener.