Repairing resin tank using Sylgard

I tried to fix the damaged PDMS layer of resin tank using Sylgard, and I partially succeeded.

I removed damaged PDMS layer from resin tank using hot water(>70℃) and then reconstructed new PDMS layer using Sylgard 184 silicone elastomer base 112ml and Sylgard 184 silicone elastomer curing agent 11ml(must be mixed well).

Just after pouring the mixture to resin tank, there were many bubbles in new PDMS layer, but after 2 days(48hours), there was no bubble and cured.

I printed the crystal for test. I could print the crystal using repaired resin tank, but that was not perfect.

I think the problem is the damaged acryl plated.

Someday, I will try the replacement the acryl plate to glass plated.

Thanks for reading.

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Great job! Not sure why your print didn’t come out well.

I read somewhere that the Sylgard PDMS cured softer than what Formlabs is using. This may have something to do with it. Maybe a softer PDMS doesn’t work well with the tilt peel mechanism of the Form1.

Maybe adding more of the curing agent can solve the issue?

Monger Designs // I think my resin tank’s acryl plate(optic window) already had some scratch so my print didn’t come out well.

But maybe there are other reasons for fail of print, when I repair my resin tank I will use the different ratio of Sylgard base and curing agent to harden PDMS layer.

Thanks for suggestion+_+

Thanks for sharing your results! I’ve recoated several vats so far. The Sylguard is distinctly softer than the OEM liner. I think the softer material may work better in the Form 1. We’ll see if it lasts as long. I usually get vat damage from big print jobs that fail, creating big over-cured blocks of resin in the bottom of the vat., rather than having the liner just wear out.

I’ve been using a vacuum chamber to de-air the silicone before I pour it into the vat (after mixing, as this is when the bubbles get introduced), but it looks like they take care of themselves.  I  use a simple bubble level from the hardware store to try and get the thickness as uniform as possible. I clean out the vat as well as I can and then cut out the old silicone layer just before pouring the new. I don’t do anything to the bottom inside surface of the tank, and that seems to work out. I use a cheap digital scale to measure out the Sylguard. - 85 grams of silicone and 8.5 grams of hardener.  The specific gravity of the mixed silicone is 1.03, so it sounds like you are adding quite a bit of extra silicone. It could be affecting the cure by absorbing or scattering more light than it should. You might try lining a vat with about 85 ml of silicone base. Let us know how it works  if you try it.

Good Luck!


I’m interested in this PDMS replacement process. It seems like the PDMS in my 3 resin trays has optical distortion issues. When I look through the empty resin tank basins I notice a slight optical distortion of what ever is on the other side. This distortion is inconsistent, although there is a tendency to see distortion along the edges of the print area and some regions of isolated distortion within the print area. It helps to look at a slight angle (off normal) at the bottom of the empty resin tray, then it becomes very apparent when looking at straight edges as they become wavy and disjointed, similar to how some filters work on an image in photoshop. I’m not sure how else to describe what I’m seeing. This distortion seems to be related to failed prints because the prints seem to fail at these areas. Also, my first resin tank had waves in the acrylic on the underside surface of the resin tank in some areas, but then it seems that is only part of the issue. I haven’t printed in a week. I have been working with FL on this for a while. Symptoms: laser beam appears to be elliptical with some odd lateral fading of the beam. Maybe, this is all within tolerance, also the support structures have been deteriorating (failing to print properly or not a t all), there is partially cured resin floating around the tank and the parts are warped too. I’ve tried adjusting the build platform height (plus and minus) however the output seems to be getting worse?  Are any of these symptoms similar to print failures that you have seen before replacing the PDMS layer?

Andrew Hudson//Thanks for suggestion! In this time, I used the Low-Iron Glass(White Clear Glass) as optic window and mixed Sylgard 80ml and curing agent 8ml(I refered the article from MadeSolid blog). It’s almost done. After printing using New Vat, I will be post to my blog and here. Thanks again!

Temujin Kuechle//I think both are problem ; Vat & Resin. In the Vat, acryl optical window already had some scratch. Resin, of course, had debris of failure of printing. So, I experienced continuous failure (and frustrated…). So, in this time, I will use New Vat(which I made by myself) and New resin!!! Say again, I will be post the result to my blog and here. Please wait+_+ Thanks you for comment!

So I have 3 tanks and two were torn up so I finally gave this a try and my first one is working great!

I used a 80/8 mix I just stirred up well in a cup and poured it in.

I wasn’t in any hurry so I just left it be for several days.

I’ve got a second tray setting up now.

My acrylic looked bad too so I polished them all over first with Novus 1 and 2 mixed.

I’ve done about a dozen prints so far with my re-coated tray and it looks like it is hazing just as fast or faster than the original.

But at least this is easy and way cheaper than buying new vats!

Although it is yet another unexpected expense involved in the process…

Does anyone know if there is any way to make the PDMS mix harden more?

Every time I have a print failure that falls off it takes out a chunk and ruins it.

And with a 50% failure rate at best that means every other print ruins a tank.

There has got to be some kind of hardener that could be added?

Vince Erb - If you are having 50% of your prints fail, then I’d guess you are having the fairly common laser / optics degradation issue. Open a ticket and get it sorted out. FormLabs has been very good about working this out with me, and I am now printing fairly chunky 200+cc parts reliably. It’s a great machine when it runs right! Get it sorted out - you’ll be really glad you did.

Good Luck.

-Andy Hudson

I’m on my third machine now and waiting for a response from support on my latest issues, but yeah I have had some awesome prints when it works.

I would still really like to find an additive for the Slygard that will harden it if anyone knows?

I just printed a couple 200cc parts using a Sylguard liner. This is running on a machine with the latest optics / laser upgrades. I’m finally at a point where the Form 1 meets expectations - I can print a part, sand off the support nubbins, and make a silicone mold straight away.  I hope you can get it sorted. The pain of waiting and trouble-shooting the first generation printers is more tolerable as a distant memory while the Form 1  cranks out the parts.

I think the Sylguard 184  liner may outperform the OEM liner, as the softer material seems to put less force on the part and supports. It’s difficult to find data on tear strength  and hardness of the optically clear silicones, So I can’t tell if there is another material readily available that would be better… Let us know how it goes with the Sylguard when you are back up and running.

Amazon sells a 1.1 pound kit for $61 (with S&H). How many tank re-lines could one expect to get from the 1.1 Lb kit ?

It will easily give you 5 re-lines. You should be able to get 11 re-lines out of 2 kits,  If you already have an accurate scale, then you are looking at $11 - $13 for re-line a tank. A cheap digital scale should run $25. You’ll need to level the tank with a bubble level (just use paper if you don’t have shim stock).

I like to rest the tank on a couple blocks of wood, right on the clamped edges, to keep from scratching or smudging the bottom surface.

Good Luck with t!

-Andy Hudson

Alot better price here:

That’s where I ordered from with no problem.

Andrew, Vince, thanx for the info/link !

Like Monger suggested, trying a bit more of the curing agent might make the silicone harder, but usually it just reduces the cure time and may affect the ultimate properties of the silicone.  Another thing to try might be to just reduce the amount of silicone used to result in a slightly thinner layer-- that would have less ‘give’ since the hard acrylic is closer to the surface of the silicone and there’s less opportunity to ‘bloom’ into the surrounding area.  As long as the build platform doesn’t bottom out on the lead screw (I’m not sure if there’s a limit switch in there) I think it’s pretty tolerant of different thicknesses of PDMS.

I did use a touch more curing agent this last time in hopes that it would make it harder. Until I replace it again I’m really not sure if its any harder but it does seem a bit more resilient. I haven’t varied the PDMS thickness much at all but would agree that doing so shouldn’t be a problem. So anyway the added curing agent may have been sufficient, time will tell, but it looks good for now. In the meanwhile I’ve been waiting over a week for a reply from Formlabs on my latest support issues, but I think I have the PDMS layer replacement process pretty much dialed in now. It’s not cheap but it’s way better than buying entire vats!

I also had success printing the rook on the first attempt using the formlabs white resin and the sylgard 184 silicone. I removed the original silicone using an X-acto knife and it pealed out very easily. I checked all the edges to make sure every last sliver of silicone was removed. I then thoroughly cleaned the tray with isopropyl and let dry.

Using an old home depot bucket and lid I drilled a hole and attached a fitting to my vacuum pump. I poured 80 grams + 8 grams of catalyst for a total of 88 grams. Make sure to weigh the original silicone so that you know how much will be poured. For me, it was about 65 grams. You can weigh the batch as you get close to your target number to make sure you get the exact amount. If you go a little bit over it’s ok, you can calibrate the build platform up to 1mm higher if necessary.

After mixing the silicone for 5 minutes I poured in the appropriate amount, then placed the tray inside the bucket and used a bubble level to level out the tray. I placed the lid on and drew a vacuum only to about 3 inches of Hg, not very high, because if I go any higher the walls of the bucket will implode. After only 5 minutes in the bucket 99.9% of the bubbles were gone. The bucket would hold a vacuum for about 1 hour. So, I ran the vacuum pump 2 more times spaced by 1 hour. I let the silicone cure over night (24 hours total) and tried printing with complete success!

I highly encourage people to recycle their resin tanks at least once. Don’t forget to use enough isopropyl to get it 100% clean of residue. Also, use a small piece of tape or a marker to record how much you needed to raise or lower the build platform in case you need to switch between resin tanks.

Before pouring any resin in the resin tank, start printing a part and pay attention to the build platform to make sure it come sin contact with the silicone. If the dry tank doesn’t stick to the build platform a little and make a “thud” sound when pealing then you haven’t lowered it enough. After you add the resin the “thud” will go away and it’ll peal just like the original silicone.

Good luck and happy forming!


Just having a go with the sylgard, hopefully will be able to see if it’s been successful tomorrow.

Hey thanks that actually sounds perfect! Looks like its a little more expensive but I may give it a try next time.
I’m having a really hard time coming up with money for resin even right now though so it will probably be a while.