IPA lifespan with FormWash

I’m using 99.9% IPA - always have, as it seems the easiest to get hold of. With FormWash, the parts are coming out sticky/tacky with all resins (tough, tough1500, durable, white…) after the IPA’s been used for less than a dozen parts. I even go to the trouble of wiping down all the loose resin from the print bed around the part that I can, before washing.

A dozen washes, then I need to swap out the IPA seems pretty poor going. I’ve never had a clear reply from FormLabs about what IPA they really recommend - the answer’s always a bit wooly. Is 99.9% too strong? Is a dozen washes all I can expect, then have to chuck away all that IPA?

I’ve also observed that used and siphoned IPA “settles out” to fairly clear again after being left for a couple of months (stuff I was supposed to dispose of, but forgot) – has anyone tried carefuly siphoning off this clear IPA again and reusing it?

Washing is one part of the FormLabs process I really don’t like and believe always ends up with my parts wose than they should be - with either resin-dribble runs (always bad with durable) or with resin clogs (always happens with Tough). Advice appreciated.

They used to advise a higher concentration, but reduced the official recommendation to “90% or higher” (except for biocompatible, which is 96%+).

Weakening the concentration won’t improve your results. Disposing the old alcohol and replacing it with fresh stuff will.

How many washes you get really depends on how much excess resin is going into the bucket (size and surface area of part, amount of residue on it, whether the geometry has cavities where resin pooled). If you remove the parts from the build platform first, and use the wire basket, that may stretch the working life of your wash solution by a bit.

You could also consider a manual “dunk bucket” - i.e. dip your part in a “dirty”, pre-wash bucket first, even let it sit there for a few minutes, before placing into the Form Wash. That would greatly reduce the amount of excess resin contaminating your Form Wash each time. Before the automated wash station came out, some folks would maintain a “dirty” initial bucket and “clean” final bucket. When the initial bucket became too dirty they’d dispose of the contents, clean it, fill it with fresh alcohol, and that would become the new “clean” bucket with the moderately used alcohol in the other one being demoted to the “dirty” role.

Age plays a factor as well. Like you, my partially-contaminated alcohol sometimes sits unused for months at a time and gets a bit gross. Big bits do settle to the bottom and congeal, so siphoning off the top may let you stretch it a little, but I’m not sure it will be worth it. As resin dissolves the whole mixture becomes less effective.

Another thing I’ve noticed helps is keeping some pristine alcohol in your rinse bottle, and giving parts a squirt with it right after they come out of the Wash - especially any nooks and crannies. You can use an alcohol-soaked Q-Tip with a wiping motion at the same time - a bit of mechanical cleaning action is really effective at removing tackiness. Note moderate amounts of lingering tackiness will completely go away after a full cycle in the Form Cure (or other UV oven).

Finally, you might consider switching to TPM - I hear it can absorb 3x the amount of resin before needing replacement.


Thanks for the response. Manual washing and grotting about is what I what I was sold the FormWash for - just straight from printer to wash to cure. Obviously that’s a mis-sell. Perhaps two FormWash units would be more reaslistic - particularly in light of the manual wash process being a two-bucket process.

Regarding poking around with a Q-Tip - that’s exactly what I’m having the issue with because my workflow is to only remove the supports after curing, manu areas are inaccessible until that point, so can’t be manually poked – so any uncured resin that congregates in the part and isn’t washed out is getting cured.

The tackiness I have never goes away. I’ve even tried double sessionss in FormCure - nothing seems to be able to stop parts being sticky. My customers complain as the parts are just not very nice to handle.

The only real solution I have seems to be to go through gallons and gallons of increasinbly expensive IPA… not practical or environmentally sane.

You suggest TPM. I’d been hopeful of this when FormLabs announced it, but ever since then they appear to be repeatedly deprecating it with phrases like “only use TPM if you can’t use IPA”. It’s also more expensive than IPA for me.

You may find this of assistance - this is the workflow that we use:

1: Remove print from build platform
2: Put print (complete with supports) into the “rough” clean up container, which has two aquarium air bricks in the bottom and bubble air through for approximately 1 min. We now use DPM for this but did use IPA for a long time, we would only change the IPA in that bucket after approximately 4 Litres of print resin had been used. The latest batch of DPM has cleaned up parts created from approximately 10 litres of resin and its still going strong.

The air bubbles certainly help remove resin quickly.

3: Ultrasound clean using DPM, the time will depend on complexity but is never more that 6 min

4: Clean any residual DPM from surface by putting in final bucket of IPA, again bubbling air through it for approx 30seconds. IPA in this bucket lasts ages!!

5: Gently dry with airline

6: Postcure.

Very quick, and very easy.

DPM is a better solvent in our opinion than TPM (Greater solvent action of DPM, thats why TPM does not attack the powder coating on the Formwash, yet DPM does)

Both TPM and DPM are much better than IPA if used properly as part of the cleanup. We now only use IPA to wash any residual DPM from the surface (not uncured resin) as it evaporates much quicker than water being used to clean up any residual DPM, or just simply DPM being left to evaporate on its own. Both DPM and TPM outlast IPA by many times

The additional extra expenditure on DPM or TPM as against the price of IPA, will repay itself very quickly after any batch of printing, as it last much longer than IPA,

Formwash pluses - it looks nice!!


I’m doing a very similar process to @Dxxxx… Except no rough bucket before hand with a bubbler… Although I have one an am thinking of how to integrate it into the form wash to increase agitation.

I haven’t used this new process enough though to say how effective it is yet. I’m doing 10 minutes in dpm and 5 in ipa

I posted this info some time ago, forgive the repeat. I switched to TPM and haven’t looked back. Far better results if you have resin trapped in small crevices. I use two Form Wash units, one course and one final wash. For a long time the final wash wasn’t needed. TPM it doesn’t matter how long it’s washed for. You can rinse the washed parts in water. Haven’t had to replace the TPM yet, but did need to add a clean final wash. No headaches from alcohol fumes, no fear of fire, good move all around. I used to think some resins just didn’t work well, TPM cleans them in ways that alcohol never did and shows the resins were just fine, it was the cleaning that was the problem. Hard to buy it in small quantities for reasonable price though.

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That’s very interesting and encouraging to hear! What resins do you typically use with TPM @nsherman ? I’m mostly using Tough, Tough1500 and Durable and they have the worst tackiness issues - worse than Black/White/Colour. I’m definitely inclined to consider two wash units. The improved safety and reduced smell of TPM would also be advantages for me.

@leonhart88 Interesting to hear you’re contemplating Form Wash hacks. Before the product came, out I envisioned a washing unit that flowed a steady stream of IPA along the part (think: fish floating against a grate in a river) or sprayed it from many angles (like a shower or jacuzzi), with contaminated resin passing through a filter before cycling back.

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Ive just bought a form 2 so have the pain ahead of me - however in another life I run an industrial laundry - and did a lot of surfactant chemistry.

The Idea of trying to clean things in two baths seems crazy and naive To
Me (and yes - I know formlabs tell you to do this).

Why ? Because every time you take your contaminant and dilute it in the vat of cleaning fluid - when you take the object out it has a covering of that diluted liquid from the tank you now have to remove.

Say - you add 1 part resin to 9 parts diluent in the first vat - when you take it out - you are covered in 10% “dirt” ie 90 % of the resin has been removed but you still have 10%. If you do the same in a second tank - you’re now down to 10% of 10% - ie 1%, pretty good but a third vat gets you to .1%

Ok I’m making up numbers - but the point is you have a benefit of NUMBRr OF RINSES which is way more important than anything else. Optimising an individual rinse won’t be half as important as simply adding another one, and a corollary is- if your solvent is limited - stock it in multiple baths - don’t have one very deep bath …

@Jonnyhifi your reply starts off sounding like you’re suggesting using 2 (rather than 1) wash is no use. But then you apepar to be advocating 3 washes by the end. 1 wash, with fresh IPA, works perfectly well. It’s just when the IPA starts getting “used” that the problems start

When you start using your Form2 (And FormWash?) you’ll find out just how evilly sticky the resin is. I’m not sure it’s quite comparable to laundry.

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Hi I get @Jonnyhifi. All cleaning processes where you are dunking are all about the dilution of “dirt”. Even in the microelectronics industry we have a more refined version of the industrial laundry, It is all in the rinsing, We used to do final rinse in boiled off vapours that were super pure!! Not doing that in my print lab though.

In the print lab we:
Drip off excess resin at an angle for as long as your schedule will allow. This is most important step to stretch out your cleaning solvents.
We clean in TPM and ultrasonics,
First wash is 3mins degass plus 3 mins hi
Second wash clean TPM 3 mins degas plus 3mins hi
Third wash clean TPM 3 mins degas plus 3 mins lo
Wash in warm water and fairy liquid. Dry v slowly at 45-50 deg
You mention Tough 1500, we find it slightly tacky before final cure.
We now quick rinse in clean IPA to draw off moisture to save time then cure. This IPA rinse lasts forever thank goodness.

We use this process on MODEL, TOUGH, TOUGH 1500, and CLEAR
DENTAL SG we use just IPA not TPM.

Hope that helps.

We are very fussy about cleaning as we print v small components and this cleaning works and is quicker than a reprint that is typically 10 to 14 hrs!!!

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What does “3 mins degas plus 3 mins lo” mean?

Sorry did not explain well.
My ultrasonic cleaning tank has a degas setting that gives short bursts of ultrasonics to degas ie to remove air and air bubbles from blind holes and the cleaning fluid. It then has a high (HI) continuous ultrasonic setting and a low (LO) continuous ultrasonic setting

So 3 minutes cleaning at degas setting followed by 3 minutes cleaning at the low setting. If you have small parts you can use small amounts of cleaning fluid in “jam jars”. but not with IPA, we use vented steel “jam jars”

Hope that helps. If you are interested in small ultrasonics cleaners I can give you the model I use I now run two small 2 litre tanks.

Hope that helps

Ahh. Ultrasonics does sound more thorough than the gentle tickling that FormWash applies.

thank you greymatter, I like your style and indeed what you describe is exactly my thinking. It’s indeed not just laundry : it works for batchelor cooking (getting the last Ragu out of the jar : best done with 3 swishes of a very little water each time, rather than the same amount of water in one go … or cleaning paint brushes… etc etc) !
I’m thinking of using a (couple) of old magnetic stirrers I have lying around, and rather than using IPA : getting some DMP (it’s a fair bit cheaper than IPA or TPM) rather than TPM. From what I read DPM dissolves resin better than TPM and IPA, and isn’t so likely to burn the place down… lol
I’m thinking 2 pots in sequence with DPM : then a third with water/ a little detergent, to remove any DPM.
I was thinking it would be possible to arrange to put a bit of filter paper between the magnetic stirrer and the parts above (I was thinking of running up a simple little thing using solidworks/ my fdm machine in nylon say ) so that the magnetic stirrer swishes the fluid around, and also any bits get trapped. Any idea if anyone has done this ? Seems a trivial thing to do…

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Thanks Jonnyhifi, Now I could be misunderstanding your filter paper concept, but I think that it would disrupt the vortex that the magnetic stirrer sets up.
Now going back to a previous life again involving blending of viscous resins, If you have SW and can FDM Nylon, how about designing a magnetic impeller that draws in cleaning fluid from its circumference and as it spins, jets it upwards through the middle of your jar. This method does assume your parts are suspended in the fluid. this sets up a circular flow from bottom to top in the middle and top to bottom around the edge of your jar, like a donut.
You can set up the flow in the opposite direction if preferred.

When the impellor gets gunked up, print a new one.

PS hope you cleaned out Ragu jars thoroughly before cleaning brushes in them!

Did anyone try the alternitives from the Uncle Jessy video.
They seems very promissing and much cheaper than IPA

interesting : I was thinking about the filter paper, and realised it does create huge back pressure of course : which is why air filters for cars look like something a frenchman would play a tune on to woo his sweetheart.

Perhaps filter paper is a bad idea. What sort of sized particle detritous gets mixed up in these baths ? I guess if I fdm something, I could print a mesh like structure easily enough, albeit the hole size will be very large compared to filter paper. What sort of size particles are worth taking out of a cleaning bath to ensure bits dont deposit themselves on prints and screw them up?

I went through a phase of filtering the ipa that I cleaned DENTAL MODEL prints in to see if I could filter out the solids.
I had the following filter papers and what they would filter down to:
20 to 30 microns
10 to 20 microns
11 microns
7 microns
and 2.5 microns
My intention was just to filter solids as I know I cannot filter out uncured resin. I filtered through a sequence of finer filter grades.
Solids were being removed very slowly, but the ipa was still cloudy!!
My conclusion: Experiment was worth doing but not a useful outcome!!
I got quite good at folding the filter disks into neatly concertinaed conical filters!.
If you are uk based, I can post you some filters.

For general filtering of resin say in the print tray, I use paint strainers with a 190 micron mesh.

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I am in the UK, and curious for sure, but it sounds like filtering the solvent will be a very unrewarding experience sadly.
Did you find any of the coarser filters collected much ? or did you have to go very fine before anything much was caught?
it’s clearly much easier to filter solvent than it is resin. It’s a shame they didn’t build in some kind of slowly circulating filter to pick up any junk, rather than the operator have to go in the mask and wellies when it’s all gone wrong… Maybe they felt that you’re only likely to see big bits left in the tank if things have gone wrong, so a filter wouldn’t help much, as large pieces won’t be very mobile, esp considering the viscosity of the resins.