Cleaning INSIDE the resin tank

I’ve read through the resin tank care page and it doesn’t actually give specific instructions on how to clean out the inside of the tank - only the outside and bottom.

I want to clean out a tank that I’ve used for clear resin so that I can use it for white resin. Is there a specific way to clean the inside of the resin tank without damaging the silicone surface? Or am I able to just pour the white resin on any left over clear resin?

I would just squeegee the tank with the scraper until there is almost no clear left. Then pour in the white and mix it well.

Scrape out all that you can then I would leave it propped up at an angle if possible so the rest can drain out of it’s accord. Don’t rub the PDMS layer and don’t use IPA.

You shouldn’t have any issues going from clear to white but I’ve found going black to anything else is a right pig. I have a resin tank for each colour but only one build platform just now and have noticed a slight black line in white if I go black to white. Just means I have to be extra careful. Hoping to get 4 build platforms and keep it all separate before long.

I have been told by FormLabs tech help to not mix resins. So far I have gray and castable. I have separate tanks for both.

Has anyone found a way to deal with the fogging/haze in the tank bottom other than replacing the tank. Mine only has three builds on it, very small parts, and it is getting foggy/hazy?

There are various posts on replacing the PDMS layer on here

I just bought another platform in addition to a separate tank to keep my grey and cartable resins separate. I don’t want to contaminate either of the parts.

So what I’ve done to reuse a resin tank was to scrape as much of the old resin out using the scraper provided in the cleaning kit. I would scrape the resin into a corner of the tank so it would pour out smoothly. This was advised by Formlabs support. I made sure to scrape out what I could from all of the sides and bottom surface of the inside of the tank. It’s a really tedious process, but now I switched from clear resin to white resin with the same tank.

The printing results aren’t the greatest as I need to avoid using one corner of the tank in order to get successful prints. Having that in mind, if you really are in need to reuse one of your tanks instead of just buying a completely new one, then it is definitely possible.

Ultimately, I think the best solution really is to use a separate tank for different resins. I’ve only switched from clear to white - I cannot speak for any of the other resin types.

If your using different resins you should really get a separate tank for each.
Be really really careful when taking the resin off the pmds (soft silicone layer inside the tank) and don’t squeegee it dry and end up scratching it. I had polished my scraper so it is super smooth and when I clean my tank I drag the scraper just one pass on cleared areas. Many here store their resins in the tank but I choose to empty the tank when I am done. I have found it easier to remix the resin and pour it back in and not have the pigments settle on the pdms.
Some rinse the inside of the tank with IPA but prolonged exposure of IPA on the acrylic walls of the tank will break them down and make them brittle. Also note that too much IPA can work it’s way under the pdms layer.

@Merlyn_Edgecomb I’d like to know that as well. I’ve noticed recently that my fog or haze is pretty bad so I ordered some new tanks. In the past I would just stir it up a little bit with the scraper until it was clear but now that I’m not printing as frequently (sometimes weeks in between prints) it seems like that problem is unavoidable, despite the UV protective case :frowning:

Ive read that sitting reason causes that so I’m curious what is the maximum time between prints I should be taking? Or is this something where you should just stir your tank every single day as a precaution?

I only got two prints on a new tank and it is foggy and failing. Changing out PDMS layers as often a it seams folks are doing is not a fix, it is a band aid. FormLabs has a problem and needs to address it somehow. I bought three tanks and I am now down to one and have only produced a few prints. I can not afford to keep buying tanks and replacing PDMS layers. FormLabs owes the user community some sort of plan to fix this problem.


Fogging doesn’t necessarily mean the tank will not work; it is not a binary indication of PDMS health.

If you are having endemic failures in features that correlate to fogged areas of the PDMS, then you may need to replace your tank. We have printed on some very foggy PDMS layers here at HQ with results that are not distinguishable from a fresh PDMS layer.

I know this is likely not the answer you are looking for, but I hope it helps, regardless!

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I have another question about fogging @Aaron_Silidker. I mentioned I noticed fogging on the PDMS layer of the tank but I’m usually able to gently scrape it enough to the point where it is mostly clear if not all the way clear. Am I essentially loosening up partially hardened resin when I do this and is that a possible reason for failed prints since that potentially bad resin is then being used to build my model?

I have a couple of new tanks on route but I’m curious if I could save this tank by somehow removing the resin that is in it and replacing it with fresh resin. I’ve just always been so apprehensive about leaving resin in the tank when the machine is not in use. I know the UV case protects it from hardening but obviously there is still a chemical change happening or I wouldn’t have to scrape the PDMS like that.

Just wanted to get your thoughts on that. Thanks!


What color resin are you using? Is the fogging that you notice that you can wipe away on the entire surface of the PDMS, or only in areas that you have just printed?

I’m using the white resin. To answer your question the former. The fogging I can wipe away seem to be on the entire surface of the PDMS. If there is a failed print, there is always that hardened sliver on the bottom that you have to scrape up but this seems to be a thin film that coats the entire surface of the PDMS. Looks and feels different than failed part remains.


That is the white pigment from the resin that settles onto the bottom of the tank. Use your scraper to mix it into the tank and it is totally harmless.

The sliver that you are scraping up is likely hardened resin that did not adhere to the print. Please see this support how-to on cleaning up failed prints.

If you need any more information, pleas let us know!


Ahhhh thats fantastic news! So out of curiosity is it good practice to stir the resin in the tank every day just to avoid any issues or is that simply OCD paranoia on my part? Haha

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It is a good idea to stir the resin in the tank before a print. It is also a good idea to filter resin that has been sitting in the tank for a while or has been used for many prints. Fresh, clean, well mixed resin makes the results much nicer.

This is what we need to do. Best to pour it back into the bottle via paint filter.

Formlabs told be to not pour goop from the tank back into a new/partially used bottle. Pour from the tank into another bottle. Keep new and “used” separate.