Measuring IPA’s Resin Concentration

As more parts are cleaned, the IPA gradually becomes more concentrated with liquid resin, reducing the effectiveness of Form Wash. Replace IPA when the wash is no longer effective and when parts have tacky surfaces after washing. Use the hydrometer to check the IPA’s resin concentration between cleaning cycles and help determine when to replace IPA.

Wear gloves when handling parts and surfaces with IPA or uncured resin.

Determining When to Check the IPA

If part surfaces are tacky after washing and drying, the IPA may need to be replaced. The Form Wash hydrometer can be used to measure the alcohol’s resin concentration as another indicator of the effectiveness.

Testing at Formlabs indicates that parts may start to feel tacky when coming out of an IPA solution that is 5-10% concentrated with resin. When properly calibrated in fresh IPA, the hydrometer included with Form Wash recommends replacing resin at around 10-12% concentration. Depending on the sequence, part size, and volume of solvent, up to 200 parts can be washed before emptying and fully replacing IPA.

TIP: To significantly prolong the lifetime of the alcohol before replacement, consider implementing a preliminary rinse with a small volume of alcohol before inserting printed parts in Form Wash.

As IPA evaporates, add fresh IPA to keep the fill level between the minimum and maximum lines.

About the Hydrometer

The hydrometer must be calibrated in fresh IPA. Calibrate the hydrometer when first adding IPA to the wash bucket or when the IPA is replaced with a different concentration of IPA. The hydrometer is designed to work with 90% IPA or higher and will not work with IPA less than 90%. After calibrating in fresh IPA, the hydrometer is only effective for measuring IPA of the same concentration. The hydrometer can also be calibrated in a smaller container of fresh IPA.

Reference the components of the hydrometer according to the following names: A. O-ring B. Float C. Handle D. Tall Wings E. Short Wings F. Weight

Checking the IPA’s Resin Concentration

To check whether the IPA is suitable for cleaning parts, lower the mount, open the outer lid, and float the previously calibrated hydrometer in the wash bucket. Note the alignment of the O-ring relative to the float’s wings.

Reading the Hydrometer

When calibrated properly, the O-ring should be set to align with the short wings in fresh IPA. As the IPA’s resin concentration increases, the weight will float higher, and the stem and O-ring will rise. For a smooth, dry surface finish, replace IPA when the O-ring rises above the float’s tall wings.