Toll Free: 800.643.7822

Type of Water to Use on Soldering Sponges

Question: Are there any benefits to using deionized water versus tap water on the solder iron sponges? What is the best type of water to use?

Answer: This is a great question, as there are many differences between water from various sources. In order to make the water more consistent across all the uses, especially the way it is used in electronic soldering for the cleaning of soldering irons, the deionized water is the best thing to use as it the purest of the waters. I’ve attached a web site, which I found interesting, where the discussion goes on between the use of DI vs distilled water and I’ve paraphrased some of the statements from the site.


Regular tap water has many ionic impurities and minerals which will react with the soldering iron tips. The impurities found in water include suspended particles, dissolved organic and inorganic solids, microorganisms, viruses and DNA.

“Two of the most common processes used to remove ionic impurities from water are distillation and deionization (DI).”

“Distillation purifies liquid by boiling it, capturing the steam and then condensing the vapors. The condensed vapors are then returned to their liquid state finishing the distillation process. Solids and other contaminants, salt being the most important, remain in the original container with just pure water being reduced to vapor.”

“Deionization removes minerals and ions, both cations (positively charged ions) and anions (negatively charged ions), through a chemical process. DI uses specially manufactured ion-exchange resins which exchange hydrogen ions and hydroxide ions for dissolved minerals, which are then recombined to form water (this leaves DI in an unbalanced condition and with an electrical charge.)”

When to use either?
“Because distilled water is pure, it’s valuable in research since it is a constant and does not interfere with any chemical processes. Distilled water is used primarily as a solvent for reagent preparation, as a calibration standard or analytical blank, for cleaning testing equipment and rinsing an analyte. Distilled water is used when making High Purity Water. It should be used in all equipment sterilization.”

“Deionized water is used when an application requires a soft solvent. DI water works best in cooling applications because of its lack of mineral deposits. Deionized water is also used in reagent preparation, transferring an analyte within a test procedure, as a calibration standard or analytical blank, and for cleaning lab equipment. DI water is best for washing glassware because of the absence of minerals and ions. DI is corrosive and should not be used when there will be extensive contact with certain metals.”


Deionized water is deeply demineralized, ultrapure water with the resistivity close to 18 megohm-cm. It is used in microelectronics, printed circuit boards, instrument manufacture, pharmacy, washing liquids, etc.

In order to obtain the high quality pure deionized water, a multi-stage water purification process can be used. After pre-cleaning, the water is supplied to the reverse osmosis membrane, and then the water is filtered through a special deionization medium, which removes the rest of the ions in the water. The purity of deionized water can exceed the purity of distilled water.”

After going through this information, the reasoning for the use of DI water is its consistency, regardless of where you are globally. Through the years I’ve seen the use of all types of water, DI, distilled and tap water. The tap water was the worst due to the various sources for the water and the variation in the water hardness itself from any location. By recommending DI water, this variation is eliminated as DI water is the cleanest water electronically.

The use of water in the sponge to clean the soldering iron tips also has some other disadvantages, due to the steam cleaning, which happens when the hot soldering iron tip is placed onto the damp or wet sponge, creating a thermal shock to the plating on the tip and many times causes the plating to crack. When this happens the tip deteriorates very quickly, especially when using Lead-Free solder. This is why many of the solder iron manufacturers provide a brass pad to clean off the solder, which is to prevent this thermal shock and extend the life of the tip.