# Weight of a print vs. volume of a print

I’m guessing that since the resin curing process is chemical, it doesn’t “cook off” any volatiles, if I know how much a ml of resin weighs “wet” I know how much the same volume weighs when cured. So the question is, what is the weight per ml of uncured resin?

It looks like there’s a posting that says an empty 1L bottle weighs 120g, and full it weighs 1200g, so 1L of resin is about 1080g by this math… 0.92g/ml, slightly less dense than water. I know viscosity and density don’t have to be related to each other, but the resin seems like it wants to be denser that that.

I’m making parts for use in small radio control aircraft, weight is important, and I’d like to have a better idea of what to expect before I print, than go to the trouble of printing and weighing to find out…

So, anyone have a weight per ml of cured resin (in this case, grey)?

It should be the same cured as uncured.
Curing is a polymerization process, there is no evaporation and there should be very little volume change (you don’t want a resin to change volume during curing, or the print will crack, warp, or otherwise lose its shape).

Yeah. That’s what I figured. So if it’s correct that a 1L bottle of resin contains 1080g of resin, my answer is 0.92g/ml…

Experimenting is the FormLabs way.
A full bottle of Grey02 weighs 1181g and and empty bottle weighs 107g. That means 1000ml = 1074g. So the density is 1.074g/ml.
Now the metric GRAM was based on water as I recall, so a bowl of water would be 1.000g/ml. I put a part in water and it promptly sank. So Grey02 resin is heavier that water. All seems square.

Now my calculated density is assuming there was precisely 1000ml in my bottle. Of course that is not true. To find the perfect answer you would need to measure the volume yourself and weigh it yourself with good equipment.

Not really. 1 liter = 10 cubic cm. There is no connection to water.

There cannot be, it defines a volume of space, not volume equivalent to weight of some substance.
Density of water is a little under a 1 g/ml (0.999something at room temperature).

Anyways, when measuring, also bear in mind that different resins (or even different batches) can have slightly different densities as well. I’m guessing that even not shaking the bottle well before pouring into a measuring cup will produce a discrepancy.

Ante, I think you’ll find that 1 Liter of water is 1000 Cubic Centimeters, not 10. One cubic Centimeter of water is equivalent to one milliliter of water. Also, a lIter of water weighs one kilogram. Therefore, a cubic centimeter of water weighs 1 gram.

I did do my math wrong, though. If a 1L bottle of resin contains approximately 1080g of resin, the resin is more dense than water. By approximately 8%.

JoshK, I love a true empiricist. Thanks for the experiment to confirm that resin is indeed denser than water!

I edited my post, I should have said gram not ml. I know 1ml = 1 cm3, that’s just volume. I meant water was used to define weight. I backed it up with a quick google search.
Wiki: “In the original version of the metric system the base units could be derived from a specified length (the metre) and the weight [mass] of a specified volume (1⁄1000 of a cubic metre) of pure water.”

You’re right, sorry, meant to write milliliter, not liter.

1 milliliter is not 10 cubic cm either, it is 1.
Sorry I couldn’t resist

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LOL, you’re right.
Messed it up completely. No idea where that came from.

Anyways, 1000 ml of water = 999.97 g.
So yeah, resin appears to be just the slightest bit denser than water (incidentally, that is why it was possible for a few experimental SLA printers to use saline solution to float the resin, instead of printing on PDMA, teflon or acrylic).

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@Ante_Vukorepa that’s very interesting, I was wondering if that was possible. I even floated some resin on saltwater to check exactly that - so how did those experimental printers work out?

It seemed to me like a great way to have old school SLA without peeling and minimal-or-no supports - and yet also not have to fill an enormous VAT of resin… Why didn’t they work out - or did they?

Not quite sure. I’ve read of people experimenting with that on various DIY SLA fora etc. but never saw anything commercial or semi-commercial. The Peachy Printer, the tiny sub-\$100 SLA open source printer was supposed to use that trick, not sure how that went. I do know someone who backed it and got the beta kit (i think) so i might ask them.

It’s using MakerJuice resin (AFAIK), so nothing magical about the formulation either. I don’t see why it shouldn’t work, apart from issues with vibration and such.

I saw a video on the peachy printer once, it was obvious they were using crappy camera work to disguise the fact everything prints in the shape of a cone. They don’t compensate for the surface of the resin getting closer and closer to the laser source.

Peachy is more of a desk toy or a proof of concept than anything.
The whole point of it is to keep everything brutally simple and cheap.