Recoating the Tanks with Sylgard

For the past year or so, I put aside all the used tanks from my Form 1+, and even bought a few used ones for a cheap. This past week I finally got with the program, and bought a package of Sylgard 184 and began recoating my used tanks.

First let me say, this is a pretty simple and easy job t do, and it save you quite a few $ over buying new tanks, although they don’t last forever and sooner or later, you’ll have to buy new tanks anyway.

Here is a very important thing to know for those that are storing their used tanks for future reconditioning. Either store them without the black cover on, or make sure the edges and side of your tanks are clean. If there is any resin trapped between them, over a period of time, that resin will harden enough and stick to he cover and side of tank, and when you’ll try to get it off, you WILL break the top edges of the tank. No amount of soaking in soapy water will prevent this from happening.

I was able to salvage 3 tanks out of 6 that I had stored. Aside from the Sylgard the only tools you will need are a pair of tweezers, a level, a scale capable of measuring in grams, and a container to mix the Sylgard in

Removing the original PDMS is about as simple as it gets. I sued a pair of tweezers to grab a corner and lift the whole layer off. I then weighed the old PDMS layers They all came up to 63 grams. I’m not sure, but I seem to remember some say that over the life of the PDMS, it actually looses some weight, and since just about every FAQ I found on recoating mentions 65 grams as the amount needed to recoat, I would assume that 2 gram difference accounts for that loss.

Some FAQs suggest cleaning the clear acrylic on both sides. I suggest cleaning the bottom of the acrylic only, then once you remove the old PDMS, put a cover on the tank until you’re ready to refill it. The only thing I did was to inspect really close to make sure there are no little pieces of the old PDMS still stuck anywhere. But it should already be as clean as it gets, as that surface was previously sealed under the old PDMS. No sense in possibly introducing any micro scratches or smudges. It was clean enough when the original PDMS was added, it’s just as clean now.

For the sake of easy match, I measured 190 grams of Sylgard, the added and additional 19 grams of the hardener. I mixed everything for about 3-4 minutes making sure I rotated the container every few seconds and scraping the liquid from the sides to make sure every thing was thoroughly mixed. I then poured 65 grams in the first 2 trays, and then I was barely able to scrape off 65 gr for the last tray. Depending on the size of you mixing container, you may have to mix a bit higher quantities. If I had to do it again, I would go for 200 + 20 next time.

Anyway, you’ll have to manually tilt each tray to make sure the coating covers the glass and the edges of the tank, then place them on a perfectly flat surface. Use an actual bubble level, do not rely on a digital/Phone level app. The big fallacy of those apps, is they only work AFTER they’ve been calibrated on a perfectly level surface, so they pretty much require a bubble level to start with.

Back to the filled tanks. During the mixing, there will be millions of micro bubbles in the liquid, and I don’t have a vacuum chamber to degass it. I saw someone mention they used a hair drier to remove the bubbles, and I tried it too. Unfortunately that only works on larger surface bubbles, it has no effect on the micro bubbles inside the liquid. So I was a bit worried, but after a few hours, all the bubbles were gone. Apparently no degassing is needed.

So now I have 3 tanks waiting for the new PDMS coat to cure. They are about 36 hours into it, and should be ready by tonight.

Once I get a chance to use one, I’ll post a followup here.

P.S. After about 24 hours, I pulled the leftover layer of PDMS from the mixing container, and the first thing I noticed is that the Sylgard is a quite a bit “softer” than the original. Maybe that will change after its full cured, maybe not. Maybe the original layer got harder due to it being subjected to use. Don’t know for sure, only an actual printing test will tell.


great job!!!

I used Sylgard on my form1+ with great results, just ordered some Qsil from a UK supplier as it’s cheaper and should be enough to re-coat 4 tanks.

Please let us know the result!

Well, first results are in, and they’re not that good.

Last Sunday evening, I gave the first tray a test. It was basically just a little over 48 hours, maybe 8 hours after getting it recoated. Put the tray in the printer, added some Grey v3, and pushed print.

An hour or so later, I was greeted with a print. Parrt of the print was successful, the other part not so much. The base was extremely thin, which means the print surface was way too close to the PDMS, or rather the PDMS layer was too thick. Aside from the partially failed print, this also had some “negative” effects on the layer itself. It left some marks on the PDS, and it also tore the PDMS away from the frame in the front right corner.

So I tried another print, in an undamaged area, but this time I adjusted the platform height to 0.5mm. The base thickness now looks more or less normal, but I’m still having problems printing.

So one piece of advice to those that are going to go the re-coating route, is to start by raising the platform a bit, and then adjusting it downwards from there. In a perfect world, the thickness of the new Sylgard would be identical to the original PDMS, but this is not a perfect world.

With regard to my printing issues, I can’t say for sure it’s the new coating, since I’ve been having all kinds of issues with this new Grey v3, so I’ll try a different resin as soon as I get some.

Right after I posted the previous entry, I pulled the PDMS off the tray and found one of the problems. It was obviously not level.

I measured the thickness of the PDMS on 4 corners: Front right corner, where it tore up, it’s 1.47mm thick, the front left corner is 2.65mm, back left is 4.27mm and back right corner is 2.92mm.

So I’m not sure what the heck happened there, but it’s obviously a big FAIL!

Then I pulled another one of the trays, and check out the wonderful surprise.

A day after the trays had cured, I put them back in their boxes and on a shelf. Assuming they were fully cured, I put the boxes up on edge, as I had previously stored the original unopened trays.

When I saw that, I also pulled the other tray I had done at the same time. It’s perfect (as far as run-off goes). So I’m at a loss as to what happened.

Back to the drawing board, I guess… Gotta love those learning pains!:unamused:

Do not give up, because they are the first ones you do, I will also do my PDMS already learned a lot with your experiences I will post mine trays to that too, a doubt when you calibrate the Z axis to a tray when replacing it the next tray will have Which also calibrates the Z axis?

Looking at the pictures above the level you used wasn’t quite long enough. The little bit of taper at the ends is likely the reason your pour wasn’t level.

Also, the material that isn’t solidified is a sign of poorly mixed silicone. Mix this stuff about twice as long as you think is necessary and then mix some more. The working time is fairly long so there is plenty of time to mix, pour, and get the bubbles out. Letting the trays cure in a warm environment helps. (I had a couple that needed to be warmed in an oven to set).

I have just recoated three of my trays with Sylgard I bought from Ellsworth adhesives here in the UK.
when I weighed the old PDMS layers I found one was 99gms and the other 103gms. So I mixed 315gms for the 3 trays and it worked out absolutely on the button. I could not scrape another gm from my cup (strangely).
Lots of bubbles in my mix but after about 2 hours they have all disappeared.
I now have to wait, at least 36hours by the sound of it.
I did try the solution from Druckwedge. That took over 4 days and in the end I had to resort to heating it. With the coast of shipping from Germany it turned out to be almost as expensive as buying a new tray.

I weighed the old PDMS layers I found one was 99gms and the other 103gms.

Yours must be Form 2 trays, because the Form 1+ trays only have about 63-65gms of PDMS. Luckily the cost of Sylgard here in the States is not that bad, at $60 shipped, it’s about the cost of 1 new tray, and theoretically I can get at least 6 trays out of it.

It looks like Ellsworth only sell big volumes of Sylgard,what size were you able to buy from them?

Here is the link
£82.71 for 1.1kg
At 100+gms per tray that should do me for at least 9 trays
If it works!!

And yes I have a Form2

That’s not such a bad price, it’s actually a bit cheaper than what I paid for mine. The one I bought is 1.1lb, not kilos, so you’re getting 2.2 times as much Sylgard for roughly $103. I don’t know if that includes VAT and how much shipping cost, but it’s in line with the US prices.

Plus VAT and shipping. Total invoiced was £110.05p

That’s good, I got a small pot from the states when I had my form1+ and I paid almost that much to do 6 tanks.

I paid $60 for one pound, so for a kilo, it would be $132. You paid £110, which is about $136. So there’s very little difference in the cost…

Sounds like a great price. About 16 tanks for $136. Nice. :slight_smile:
Still looking forward to results with the QSIL. Elastosil is another type made by wacker.

16 tanks, not really, more like 12-13 out of a 1Kg bottle.

Anyway, something else I found while doing this is that the Acrylic surface of these tanks, including the clear bottom are pretty susceptible to IPA. Do not use IPA to clean the clear surface, and if you do, do not touch the area with your finger, or it will leave a mark.

I even tried to remove the clear acrylic bottom, with the idea of replacing it with glass, but it’s pretty well glued in, and nearly impossible to remove without damaging the orange frame.

I also noticed that the acrylic itself starts to get fogged up after a while, so I don’t think these tanks have much of a life in them, I think maybe 3-4 recoatings before they have to be discarded.

I would try some Novus polish on the acrylic and then clean with glass cleaner. The Novus may clean the surface clouds.

On a side note the clouds in the PDMS need to be pretty severe to effect the prints on the Form 2. I’ve printed on a severely clouded PDMS with high temp resin and had extremely good results. (HT resin can cloud a tank very quickly by the way).

I thought the form 2 is only 65ml? So 1100/65 gets you at 16+waste material.

Acrylic and IPA or ethanol don’t go together. Applying it causes stress on the surface resulting in cracks and fogging.
Z-vats replacesthe acrylic for glass so it should be possible to remove it.

Oh and yeah, I experienced the same with HT resin. After three 100ml prints, the tank is completely clouded.