What type of water makes it difficult to produce suds?

Hard water makes it difficult to produce suds due to its higher concentration of dissolved minerals, primarily calcium and magnesium ions. These minerals interact with soap or detergent, forming insoluble compounds known as "soap scum." As a result, when hard water is used, less soap is available to generate lather or suds because a significant amount of it is used up in reacting with these minerals.

In contrast, soft water has fewer dissolved minerals, making it much more effective at creating suds with soap. Purified water, typically treated to remove contaminants and mineral content, and mineral water, which contains naturally occurring minerals, do not have the same inhibiting effect on suds production as hard water does.