Formlabs generally recommends isopropyl alcohol (IPA, concentration of 90% or higher) for washing liquid resin off printed parts. While IPA is very effective at removing liquid resin, easy to purchase, and fast evaporating, it does have some drawbacks:
- IPA has a flashpoint below typical room temperature (around 20 °C/68 °F), and therefore generates enough vapor to form a potentially explosive atmosphere in its natural state.
- Depending on local regulations, IPA may be difficult to procure or to use within buildings.
- Despite IPA’s low cost, actual operating costs may be higher than expected due to rapid evaporation and the frequency with which IPA may need to be replaced to wash parts effectively.
Depending on your use case and work environment, tripropylene glycol monomethyl ether (TPM) may be a viable alternative to isopropyl alcohol (IPA) for washing parts.
NOTICE:
Only IPA and TPM have been validated for use with Formlabs resins and accessories (such as the Form Wash). Do not use other solvents without Formlabs approval. Use of an unvalidated solvent may be hazardous to your health or damage your printed parts, Finish Kit, or Form Wash.
Advantages of TPM
Using TPM poses the following benefits when compared to IPA:
- TPM is non-flammable (flashpoint of 111 °C/232 °F, compared to 12 °C/53 °F for IPA) and non-toxic.
- TPM has a lower evaporation rate than IPA (2.3 vs. 0.0026, where n-butyl acetate = 1).
- As the solvent dissolves liquid resin, the concentration of resin in the solvent will increase. At higher resin concentrations, TPM will continue to clean parts effectively, while IPA with the same resin concentration will need to be replaced.
- TPM is available globally.
- Cured resin absorbs TPM less readily than it absorbs IPA. This means less warping and less sensitivity to soaking—parts won’t be damaged if left in a TPM bath for a prolonged period of time, unlike with IPA.
Disadvantages of TPM
Using TPM poses the following drawbacks when compared to IPA:
- TPM evaporates very slowly. Printed parts washed in TPM must be rinsed with water to remove excess solvent. Parts printed in certain resins, such as Clear Resin or Tough 1500 Resin, may come out of the water bath with a cloudy appearance. The parts will regain their normal appearance as they dry.
- Washing with TPM leaves a waxy surface texture on some resins. Post-curing eliminates the waxiness left by TPM.
- Parts take longer to fully dry when washed with TPM.
- TPM is generally available only through distributors, not local stores.
- TPM is typically more expensive per unit volume than IPA.
- TPM is not yet certified for use with Formlabs products in biocompatible applications.
Similarities between TPM and IPA
Both TPM and IPA share the following considerations:
- Both IPA and TPM (and any water used to rinse excess TPM off printed parts) should be managed and disposed of in compliance with local regulations.
- Consult your supplier’s SDS for IPA and TPM before use. Wear disposable nitrile gloves when handling either solvent, including surfaces or parts covered in IPA or TPM.
- Fully dry parts before post-curing with the Form Cure.
- Follow Formlabs instructions when cleaning Formlabs products with any solvent. Both IPA and TPM can crack or craze specific plastics.
Why use TPM?
Use TPM as a washing solution if:
- You cannot use IPA due to flammability issues.
- You cannot readily acquire IPA due to local restrictions.
- You are looking for a more economical solvent for washing prints.
- You print infrequently and find that a significant quantity of IPA evaporates between prints.
- You are sensitive to the fume smell of IPA.
Why use IPA?
Use IPA as a washing solution if:
- You want prints to dry quickly after washing.
- You can store IPA safely and/or are not limited by flammability hazards.
- You are satisfied with your current print washing process.
- Post-curing to remove the waxy surface texture left by TPM would affect your workflow.
TIP:
You can use both TPM and IPA in your wash process: wash your parts with TPM, then do a secondary wash with IPA. This yields many of the advantages of washing with TPM without the waxy surface that TPM can leave on some resins. For more information about washing prints with TPM and two-stage wash processes, read the support article on Washing prints with TPM.