How To Make a Reusable DIY Silicone Respirator Using Mold Star 20T Silicone Rubber

[@smoothon]

Smooth-On produced this video in response to people asking for a workable (not perfect) materials solution to the problem of respirator shortages plaguing many parts of the world during the COVID-19 crisis. Before responding to viewer assertions that the HEPA vacuum cleaner filter bag that we featured in our video contains fiber glass making the design unsafe, we wanted to investigate to get the facts to the extent that they are available. Kevin Egan, Head of North American Sales at TTI (parent company of Hoover and Oreck vacuum located in Ft. Lauderdale, FL) states that “I’ve checked with our product team and can confirm our bags do not contain fiberglass”. We were directed to a KZbin video made by Josh from Vacuums R Us in Arvada, Colorado to separate myth from fact based on his years of experience in the trade. Josh is very clear that HEPA vacuum cleaner bags have never been made of fiberglass. kzbin.info/www/bejne/rJ68pZKtqcZ_ec0 . We have spoken with several hospitals that maintain dedicated medical simulation device fabrication departments. Health care workers continue using HEPA vacuum cleaner filter bags to make their own DIY respirators without any reported incidence of adverse health effects. An RN that works in the Med Sim fabrication lab of one facility commented that, “at the moment, HEPA vacuum bag filters are our only option”. Our Conclusion; N95 filtration masks are optimal in fighting the COVID-19 virus. Due to the severe shortage of these masks, however, people are forced to improvise and do what they can to protect themselves, their patients and their loved ones. While we respect the opinions of others, Smooth-On is satisfied that we have done our due diligence in researching this matter. We were not able to find a single HEPA vacuum cleaner filter bag made of fiberglass anywhere. The majority are made of spun polypropylene fibers. A small percentage are made using a combination of cotton and cellulose. We also confirmed that Furnace/HVAC filters do contain fiberglass and should not be used to make PPE devices. In producing this video, we followed the lead of local health care professionals in using what they consider to be acceptable filtration in the face of the N95 mask shortage. Given a choice between no filtration and using a HEPA vacuum cleaner bag filter, we think most people would opt for the latter.

[@chrisyoung8062]

When you say "Furnace/HVAC filters do contain fiberglass" you are making a broad sweeping statement. The fact is that the high quality furnace filters such as the Filtrete 1500 filters do not contain fiberglass. Only the very cheap 1 month furnace filters, which would not work for a respirator, contain fiberglass from the research I've done. A quick test is to take a flame to the material. If it melts it is a poly spun not fiberglass. I'm not an expert and you should do your own investigation into whatever material you chose to use.

[@jimklessig8533]

I really, REALLY wish a video like this had been available when I first started using your products years ago. This video is probably the clearest, cleanest explanation of many of the trials and tribulations I had.

[@smoothon]

Thanks for watching!

[@JimBear]

Thanks again, Milo (nice apron!) and Smooth-On. Stay safe, everyone. ❤

[@smoothon]

Thanks, you too!

[@SirValak]

Awesome mate =D thanks for Creating you and your company are a Master Builder =D. Just noted the Flux Capacitor on the background at the end is mounted on killer preassure chamber

[@smoothon]

Thanks for watching, and don't forget to subscribe!

[@ropeany1]

Nice design. I think I'd use Task 8 instead for the filtration parts as that way the entire unit can go into a dishwasher or autoclave.

[@smoothon]

Good idea!

[@HAN_dMade]

Great work!!

[@smoothon]

Thanks a lot!

[@baruchspinoza4979]

I take it that you used Mold Star 20T over Dragon Skin 20 because the Mold Star 20T sets up faster and has less viscosity, thus making it better suited for mass production. Or was there some other reason?

[@smoothon]

This is correct.

[@WilSisney]

Another terrific mask design! How does the silicone mask stack up to the Task 8 mask when it comes to per-unit cost?

[@smoothon]

Cost is slightly higher on this mask

[@mainstay.]

Why develope another method, was there a problem with the method/design using Ecoflex?

[@smoothon]

This method is different in that the silicone gasket is no longer needed, but casting the parts takes longer as it is a different type of procedure.

[@mainstay.]

@@smoothon Oh good as I have just collected all the materials to make and cast the previous version, using Ecoflex and didn't want to discover that there was a problem with that design.

[@WilSisney]

@@mainstay. I just got the materials to make the Ecoflex/Task 8 masks, so I'll be giving that design a try soon. I suspect that design might be cheaper per-mask, since resin is cheaper than platinum-cure silicone, but let's see what Smooth-On says. The nice part about that Task 8 mask is that all the parts can be sanitized.

[@mainstay.]

@@WilSisney I agree the ability to sanitize Task 8 with heat is a big plus in my books. I was asking because I thought I saw someone post that the filtered opening of the previous design might be too small and allow too much build up of CO2 when one is breathing out but this design seems very similar in its area of opening.

[@LT72884]

@@WilSisney either hot soapy water will sanitize or use rubbing alcohol or bleach water. Hot soapy water is easiest for sure.

[@alexbokov7068]

How rigid is this silicone compared to Ecoflex 00-35? More generally, is there a way to get a sense of how hard or soft a Smooth-On product is from the numbers in its name?

[@wantyasapardan4029]

Hello. What is the brand/type of the 3D printer do you use? Thanks

[@LT72884]

im actually trying this method out but with Plaster of paris as the mold rather than resin.

[@smoothon]

You will probably need to seal the plaster with a clear acrylic spray such as Krylon Crystal Clear.

[@LT72884]

@@smoothon true. And im gonna use alot of vaseline so the plaster wont stick to itself haha

[@tdebreceni]

You neglected to detail for your viewers the cost of materials for the actual 65D mold, including the sculptex clay, the silicone pigment, and the aluminum shim material, as well as where your viewers may find the shim online. 65D goes for about $92 for a gallon kit, and it looked like you used about half of that for the two mold halves. That ups the overall cost of each respirator when you factor the mold cost divided by the number of respirators you make.

[@smoothon]

You are correct, there are ancillary costs which must be figured in as well. In this case one of the benefits of the casting material is that the silicone does not contribute to the degradation of the resin mold, so the more you cast, the more you can recoup that cost. The molds for the filter holder will need to be remade if a large number of castings are made, but this depends on the type of resin used, etc. You can reduce some of the tooling costs in this case by adding a filler to the resin for the rigid mold, or even using a plaster such as hydrocal (properly sealed) for the rigid mold.

[@the_arcanum]

@@smoothon Ah! Thanks for that answer Milo, I was about to ask if we could substitute 65D with a hard plaster like Ultracal 30. That will help to lower the cost of the project.

[@LT72884]

i have baked mine in the oven at the WARM setting which is 170 degrees. Bake for 20 minutes. But hot soapy water is just as good:)

[@jackyang5595]

This is really awesome

[@najib_bin_cibai]

We use air blown into silicon to demold easy...

[@smoothon]

Very good idea!

[@PaintCreateMotivate]

Do you sell these?

[@bernardoflores1832]

Does anyone know if you can buy the gasket for the mask ?

[@LT72884]

no, but just use a bead of 100% silicon caluk from the hardware store. Its skin safe and only need a little bit. Its also comfortable as well. I did this on all my 3d printed masks rather than making the gasket.

[@markk3812]

can you use mold forms from previous respirator model with mold star 20t?

[@smoothon]

It would depend on the material the original model is made of. Testing would be required to ensure there is no inhibition.

[@alexbokov7068]

I'm thinking of ordering Moldstar 31T instead of 20 to make sure the mask is not floppy. Has anybody tried that, and does it still give a good fit without a gasket?

[@Tism_me_timbers]

Anybody have any ideas on how to mold a respirator with a flange, like 3M designs and similar?

[@DaveSmith-cp5kj]

Insert placed in the mold, overmolded around the insert, pull product off the insert since it is flexible.

[@PELICANO1706]

Have you tried 3d printing the squeeze mold?

[@smoothon]

The mold itself was attempted as a print, but issues with venting and alignment kept this from being a viable option.