Carima Nontoxic Resin - Part 1 of 2

Putting Carima's "Nontoxic" Claims to the Test - Part 1 of 2

Finally, today, I am ready to try the Carima Nontoxic resin! This is a bit on the expensive side for a resin - nearly double the price of many popular brands of consumer level ABS-like resins - but I'm prioritising health over cost so for me, and many many others I assume, the slight increase in per-model costs will be well worth it, if the claims Carima make about this resin are true. 

Note - I am in no way affiliated with Carima and I paid for the resin myself. After I told Carima that I wanted to put their non-toxic claims to the test, they kindly agreed to a healthy discount for a small batch of Black and Clear resins to test out. Thanks Carima! 

For those not familar with Carima, they are a South Korean based company producing DLP and LCD resin printers, primarily focused on dental and biomedical use cases. As their business seems to be geared towards B2B, they are not very well known in the global consumer resin printer space and so its not surprising that I'd never heard of them until very recently (despite the company being 26 years old!). 

So, why did I hear about them at all? Well, it's because I stumbled upon one of their resins, which is intriguingly named "General Nontoxic"... Of course this resin caught my attention because it claims to be non-toxic and not a skin irritant, and as anyone involved in resin printing knows, PPE is a major part of the hobby due to the highly toxic nature of resins. A quick google search for typical resin printing setups will show large grow tents, extensive active extraction/ventilation setups, respirators, nitrile gloves and all kinds of (very necessary) precautions. 

In stark contrast, here is an image from the Carima website...

Yes, that is someone bathing their bare hands in the stuff!... That's some pretty big claims being made there in the image caption, so you can see why this caught my attention and I had to try it out. In fact, I'll be using an IAQ sensor to monitor the air quality next to the printer throughout the entire process so let's see exactly how those bold claims stand up in reality :)

The Setup

First up, my resin printing setup. I have a small 2m x 2m x 2m shed, which is dual layered plastic and therefore reasonably well insulated. I didn't want to drill a ventilation hole in my shiny new shed so the idea of a being able to print without activate ventilation, with a non-toxic resin, is more than a little appealing. Having said that, and in spite of the big claims being made on the Carima website, I will still be using a respirator rated for organic compounds and will still be wearing nitrile gloves throughout the process. Here is a my setup, with everything sitting on a nice stainless steel workbench.

As you can see, I have an Elegoo Saturn 4 Ultra 12k with an IAQ sensor sitting on top of it. I also have the Elegoo wash & cure stations, various PPE equipment and a new bottle of Carima Nontoxic Black resin eagerly waiting to be opened. 

Given the purpose of this initial test is to see how safe this resin is, here is a baseline of the indoor air quality (IAQ) before I opened the resin or started anything.

Take note of the TVOC level in the bottom right corner as that is what I'll be most concerned with. It was reading 0.006mg/m3 - anything below 0.3mg/m3 is deemed perfectly acceptable in a household and so perfectly fine to breath without a respirator. Levels around 0.5mg/m3 are where we should start to show some concen as it suggests poor ventilation, and readings closer to 1.0mg/m3 indicate its time to run out the door before we suffer headaches or worse. Keep these numbers in mind. 

Resin Calibration

I decided to calibrate the resin using the well known Cones of Calibration v3 model. Carima themselves have some guidance on print settings i.e. exposure times, wait times etc.  I am going to create a Part 2 of this blog post very soon to specifically focus on the calibration aspect, dialing in my printer for this resin using Lychee Slicer, and will show off all of my glorious failures, and hopefully some successes too :) This being Part 1, I want to focus exclusively on the nontoxic claims so let's skip straight to the science and see what the IAQ sensor shows throughout the printing, cleaning and curing processes.

Printing!

With the respirator and gloves on I opened the 500g bottle of Carima Nontoxic Black resin and poured it into the tank. I had sliced my Cones of Calibration v3 model using Lychee Slicer and copied it to a USB drive, which was now inserted into the printer. So after selecting the model I finally got to hit Print! 

The model was going to take an hour to print (I had excessive wait times initially, but more on that in Part 2 later). I left it alone in the shed until approximately the halfway point, and then returned to take a photo of the IAQ sensor which was sitting on top of the printer. Here is how it looked.

Checking the TVOC levels first we can see we have a negligible increase and certainly very far below the level that would require a respirator - that's a very welcomed surprise and bodes well for our test!

However, our PM levels have risen, and given we want to see all of these numbers below 30, its clear we don't have ideal air quality in the small shed. Opening the shed door rapidly drops these PM levels down to acceptable numbers where a respirator wouldn't be needed, but given I want to keep indirect UV out of the shed I will keep the respirator on and the door closed. I also only spend a minute in the shed during a print, to check readings and progress, so it's not an inconvenience or concern in my opinion. So far so good.

Eventually the print ended and so I went back into the shed immediately to take another reading. This is how it looked.

As you can see, everything is similar after one hour of printing as it was after 30 minutes. We have very acceptable TVOC levels (a big win in my opinion), though less than ideal PM levels. Now that I was done printing I could leave the shed door open and these levels quickly dropped into normal ranges. 

It's worth noting that there seems to be absolutely no smell from this Carima resin at all. I removed my respirator after opening the shed door and expected to have some kind of obvious resin smell - nothing. Nothing at all. I've read a lot of complaints from people about the strong smell of traditional resins lingering around for hours or days, and even the smell "sticking" to things that were in the same room as the printer. From what I can tell in this initial test, that is absolutely not a concern with Carima Nontoxic resins so I'd call that another win for Carima. 

Now that we've seen the impressive lack of TVOCs from the resin, I wanted to highlight something that is in stark and alarming contrast. Take a look at the readings below.

Can you guess what I did to cause this? I opened a 400ml bottle of 99% IPA and carefully poured it into a container to use for washing, without splashing or spilling a drop. Take a look at those numbers above again - to say these numbers represent a serious health risk would be a huge understatement and this for me is the most important thing to take away from this test. 

So, while Carima appears to have solved my toxic resin problem, they have also helped to highlight the often overlooked problem of toxic cleaning chemicals like IPA. I think I'll have to find a non-toxic alternative to IPA afterall.

Conclusion (well, of Part 1 anyway)

I was keen to test out this Carima Nontoxic resin to see if it is realistic to expect to be able to have a print setup with no active ventilation and extraction system while somehow keeping the TVOC levels low. After today, I feel I can say yes, it is possible. While my PM levels did rise, I am pretty confident this was entirely due to me being crammed into half of a 2m x 2m x 2m shed and I am equally confident that a more typical shed/garage size wouldn't see this kind of PM increase. The TVOC levels are the key and those barely moved at all. A great result.

A very welcomed feature of the Carima Nontoxic resin is the lack of any smell at all, so I'm counting this as another win in the Carima column. For some people the smell is one of their biggest issues so this resin will absolutely remove that problem entirely.

In relation to skin irritation, another real hazzard of traditional resins, the Carima Nontoxic resin is offically rated as a non-irritant - that eye opening image on their website showing hands cupping a pool of resin may not be that dramatic afterall. So even though I wore nitrile gloves throughout, in theory it's not necessary and that gives great peace of mind when handling these materials and chemicals - another win for Carima.

I'll get going on Part 2 of this blog post soon, focused on calibrating the Carima Nontoxic resin for my Saturn 4 Ultra 12k printer, and hopefully printing some nice models :) Stay tuned.