Is it possible to dilute, thin or liquefy Milliput so that it flows into nooks and crannies better?

If so, is there any advice on what to use, in what ratios, and whether it will adversely effect the strength of it when it cures?

I'm trying to use it to fill gaps in 3D-printed parts where the stepper motor might have skipped or the filament just didn't bind for some reason.


Epoxy putty, including Milliput, is a mixture of liquid epoxy and filler that makes the composite the consistency of clay. The epoxy does the work of holding the mixture together and bonding it to the substrate. The filler thickens it to give it the desired handling characteristics.

Some putties, like Milliput, will be softened by water while still uncured, but that's more of a side effect of the composition than a feature. The epoxy component doesn't mix with water, it's the filler that's affected.

Water can be exploited to smooth the surface because it thins the filler and the epoxy doesn't stick when it or the surface is wet. Smoothing the surface doesn't have a significant effect on the rest of the material.

But if you mix water into the putty, some of it will be trapped when the epoxy cures, which degrades and weakens the cured material. Also, the moisture in the putty in contact with the surface it's applied to weakens the bond holding it in place. The more water you add, the more it will degrade the result.

If your objective is just a surface coating or filler for minor defects, which doesn't need to be durable and won't be subject to a lot of handling, thinned Milliput may be adequate. But it isn't the ideal solution. Epoxy-based products work best when used as manufactured; start with a product of the right consistency for your needs.

If what you need is liquid epoxy, just start with that rather than adulterating epoxy putty. If what you need is a spreadable paste, start with an epoxy paste.

  • You can use water to dilute it.

    Here someone suggest adding a little soap with the water, as this will not only let it mix better, but also increase the drying time, although I think this might be detrimental for the structure.

    Note however, that some users complain about the manipulation of this mix (e.g. here: "I tried [to] dilute Milliput and although it worked (sort of) it was messy and time consuming").

  • The ratio really depends on what you want to achieve - what works best for your application. I suggest experimenting with the amount, slowly adding more, until it behaves the way you want it to.

Alternatively, you can opt for using ProCreate Putty, which I saw mentioned here, and sounds like something that acts a bit more like you would expect of a watered down putty.

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