DIY Supermaterial Save You From Heatstroke - AND make your house, barn, shed, tractor seat, COOL????

Holy crap folks - just started watching this and skipped around. I think I'm about to have an excitement aneurysm... Could this make "thin" earth berms and whole house temperature buffering a thing???

People are saying in the comments this is the most useful YouTube video EVVVVVAAAAAR:

Oh yeah, this is awesome!  I was looking for a PCM for my greenhouse a few years back that would operate around 65F.  Glycerin is actually at that same point.  I'm not sure if his mix is better than glycerin but it's a perfect application for helping keep a greenhouse warm/cold.  Imagine a barrel of this mix with 100' of tubing coiled through it circulating water.  Heat the water on sunny days to melt the PCM, draw the heat out with the water at night.

Thanks for finding this!

Oh wow.
Now I'm curious about more.... and I HAVE ice melt!! Oooooohhhh

Thank you!! Neatest video I have seen in a long time!!

Isn't it though??? I'm so excited!!!

Imagine reworking a house so that you can have panels that open for your walls for maintenance as well as in attic and you use sheets of this to create a huge additional resistance to temperature change.

Additionally utilize the idea from Mike and place barrels of this within a home-integrated greenhouse or simply a sunning area dedicated to collecting heat - or under solar panels - you could implement incredible temperature inertia for your home and nearly remove the need for heating and cooling.

This could be an early "holy grail" for reducing/eliminating needs for forced energy expenditure to heat and cool homes in places where even humidity is high.

I believe some PCMs lose their ability to freeze/thaw after enough cycles.  Clearly water/ice isn't one of those but I wonder if this salt based one can handle a thousand or more cycles?

Greg - THANK YOU!! I can't begin to thank you, enough! You may have saved both my hubby and me, today!
Ok, y'all. Not sure my brain absorption rate is where it functions best, today. So, for those of us in the remedial science class, I have questions:

1 - To recharge the (65f/18C) cooling packs, they need to be warmed? Or refrigerated/frozen?
2 - To make them colder, still (like for keeping ice cream frozen for a long drive, or keeping a temp-sensitive food cold, for a hot-day picnic or camping trip), you'd add more table salt?
3 - If #2's a yes, any clue as to (based on his same 5C water/1C Sodium sulfate recipe) would the 1/4C = 30° extra cooling stay the same, so that an increase to 1/2C would equal a 60° cooler product, bringing it to 35°, and so on? (This would be perfect, for things you want very cold, but not frozen! )
4 - If #3's a yes, any idea at what point on added table salt, you'd reach a point of diminishing return?

At any rate, I'll be making at least a blanket, a vest, and a hat insert, for my extremely heat sensitive hubby, with the bad heart!

I think the answers are:

1.  Pretend it's funny ice.  To freeze it, get it colder than 65 degrees.  Fridge, freezer, cool basement would all get it frozen.  The colder you get it, the colder it starts off but it really excels when it hits 65 and holds there for a looong time before getting any warmer.
2.  I don't think so.  Might as well use ice/water to keep things cold for a picnic cooler type application.  The freezer packs they sell for coolers likely are phase change materials that freeze at lower than 32F so they'd be better than ice since the whole time they're sloooowly thawing out, they're doing it somewhere below 32F.

Keep in mind that normal freezers are closer to 0F.  So when you freeze water and let it get down to 0F, it takes a while to lose that cold and get up to 32 where it starts to melt.  Ice at a hotel is probably only 30 degrees, that's why it starts melting right away.

Regarding the "charge cycles", from what I can tell based on general principles of materials science and the properties of sodium sulfate-based PCMs, Ben's homemade phase change material could potentially last between 500 to 1500 charge cycles before requiring replacement.

This estimate translates to approximately 1.5 to 4 years of daily use... Or if it's cycled less frequently MUCH longer... High-quality commercial inorganic PCMs often claim 1000-5000 cycles.

(
EDIT: I noticed someone in the comments mentioned a much lower cycle limit - perhaps 100-200 cycles... I suppose we need to really look at this more carefully. It shouldn't really drop this fast I don't believe.

If this is true it still isn't bad, but maybe not quite as amazing as hoped?

IDEA: what about making this flowable and REFRESHABLE and putting it in piping around the walls and ceilings/roofs? Maybe it would be liquid enough at a certain flush temperature?
)

If it is not directly exposed to extreme conditions it could be possible to see it lasting far longer.

As far as glycerin goes, after looking at this it seems the sodium sulfate PCM could greatly outperform the glycerin. From what I can tell it could much more effectively maintain a greenhouse at about 64ºF than glycerin could.

Glycerin might be easier to work with and require less maintenance, but I think Ben's PCM is a little more cost effective. My quick calculation showed that:
- Ben's sodium sulfate PCM would cost about $375 - 715 per 55-gallon drum.
- Glycerin would cost about $404 - 865 per 55-gallon drum.

@Carla I think for your four questions:

1 - To recharge the (65f/18C) cooling packs, they need to be warmed? Or refrigerated/frozen?
Answer: To recharge the cooling packs with a melting point of 65°F (18°C), they need to be cooled below this temperature. The packs absorb heat as they melt, providing cooling. To recharge them, you need to solidify the material again by cooling it below 65°F. This can be done using ground temperature in many regions, as Ben mentioned, or by refrigeration if necessary. The key is to get the temperature below the melting point so that the material can crystallize and be ready to absorb heat again when it melts.

2 - To make them colder, still (like for keeping ice cream frozen for a long drive, or keeping a temp-sensitive food cold, for a hot-day picnic or camping trip), you'd add more table salt?
Answer: Yes, adding more table salt to the mixture would lower the melting point, making the PCM colder. This follows the principle of freezing point depression in solutions. By increasing the concentration of salt, you can create a PCM with a lower melting point, suitable for keeping items colder than the original 65°F formulation. This absolutely would be useful for applications like keeping ice cream frozen or maintaining lower temperatures for food storage during hot weather conditions.

3 - If #2's a yes, any clue as to (based on his same 5C water/1C Sodium sulfate recipe) would the 1/4C = 30° extra cooling stay the same, so that an increase to 1/2C would equal a 60° cooler product, bringing it to 35°, and so on? (This would be perfect, for things you want very cold, but not frozen! )
Answer: While the relationship between salt concentration and freezing point depression isn't perfectly linear, it follows a predictable pattern based on the equation ΔT = Kf * m * i. For Ben's PCM, starting with the original recipe (5 cups water, 1 cup sodium sulfate, 1/4 cup table salt) at 65°F (18°C), we can estimate that doubling the salt to 1/2 cup might lower the temperature to around 52°F (11°C). Further increases would have diminishing effects: 3/4 cup salt might reach ~43°F (6°C), and 1 cup salt approximately 36°F (2°C). However, these are theoretical estimates... and the actual results may vary due to the complex interactions between sodium sulfate and sodium chloride in the solution. The effect is more pronounced at lower concentrations and becomes less effective as you add more salt, potentially affecting the PCM's heat absorption capacity and phase change behavior.

4 - If #3's a yes, any idea at what point on added table salt, you'd reach a point of diminishing return?
Answer: The point of diminishing returns for adding table salt would depend on several factors, including the solubility limit of salt in the solution and the eutectic point of the mixture. Generally, you'd reach diminishing returns when adding more salt no longer significantly lowers the melting point or begins to negatively impact the PCM's performance. This could occur when the solution becomes saturated with salt, or when the increased salt concentration starts to interfere with the crystallization process of the sodium sulfate. To determine this precisely, you'd need to conduct a series of experiments, gradually increasing the salt concentration and measuring the resulting melting point and heat absorption capacity of the PCM.

Thanks, guys!! I'm not seeing me using this to cool any buildings, but I have plenty of smaller scale uses for it. I'll be playing with this, as soon as payday lets me get my hands on some sodium sulfate!

Carla Burke wrote:Thanks, guys!! I'm not seeing me using this to cool any buildings, but I have plenty of smaller scale uses for it. I'll be playing with this, as soon as payday let's me get my hands on some sodium sulfate!

I might use it to cool buildings I, too, am waiting for money. Soon as I can, I'm trying this. My mom is always hot at night, she needs an anti-heating pad in her bed!

I also have more crafty type skills than him, I can make corsets and such, and I have a vacuum sealer, and am good at 3D shapes. I might make neat hat things, or shapes that don't require a vest to hold them in place.

Thank you for sharing the video Greg! I told the folks at work about it today. There is one department that works outside most of the time. We may do the vest and cold-pack thing for them. The ingredients are easy to source. This will make it a lot more bearable working in the garden as well.

So... you need electricity to make this work.
I have none.

You don't need electricity to make it work.  Making the goo requires heat but many stoves or fires use non-electric power.  Cooling the goo below 65 just requires somewhere that is colder than 65.  Like a hole in the ground or your basement.  Give it a shot Kaarina!

I wonder if NHIL’s recipe really freezes/melts at 18 C.  It could be 23-25 C according to some sources. One Japanese paper reference for 18 C seems to use closer to stoichiometric quantities.  It also claims that by adding equimolar KCl (“salt substitute”) it melts at 4° C. I’ve also read that adding borax as a nucleating agent reduces supercooling.  I haven’t tested this yet, it’s all according to literature & theory but I’ll try to post a recipe for it soon.

Can't wait to hear back on some of the smaller build stuff!!! I think he's right, this could literally save lives.

And I can't wait to hear back on some of the bigger build stuff!

For the vehicle, whole house / building options, I do believe this might be able to be made to be passed through pipes... Some ideas we might want to think about and discuss more fully as we get our hands around this to see if it might be feasible and better than putting panels/packs in place - I'm sorry if this is going beyond "low tech" options here in some aspects!

1. Microencapsulated PCM Slurry:
  Concept: Encapsulate tiny droplets of the PCM (sodium sulfate solution) within microscopic polymer shells (This reminds me of his ULTRA white paint efforts - might help.).
  Composition: 30-50% microencapsulated PCM particles suspended in a carrier fluid (e.g., water or glycol).
  Estimated additional cost: $10-$20 per liter
 
  Advantages:
  - Remains pumpable at all times
  - Retains most of the PCM's thermal properties
  - Can be circulated through uninsulated pipes in walls, attics, and under roofs for efficient heat transfer
 
  Considerations:
  - Slightly lower overall heat capacity compared to pure PCM
  - May require occasional agitation to prevent settling
  - Carrier fluid choice affects overall system performance

2. Clathrate Hydrate Slurry:
  Concept: Use clathrate hydrates, which are crystalline compounds where water molecules form a cage-like structure around guest molecules.
  Composition: 10-30% clathrate hydrate crystals suspended in water.
  Estimated additional cost: $5-$15 per liter
 
  Advantages:
  - Forms a pumpable slurry
  - High latent heat of fusion
  - Can be designed for specific temperature ranges suitable for various climates
 
  Considerations:
  - May require additives to prevent agglomeration
  - Careful control of formation and melting conditions

3. Nanofluid PCM:
  Concept: Disperse nanoparticles of a phase change material in a base fluid.
  Composition: 1-5% nanoparticles (e.g., paraffin or fatty acid-based - he used paraffin in his previous video on making awesome tarps) in water or glycol.
  Estimated additional cost: $20-$40 per liter
 
  Advantages:
  - Enhanced thermal conductivity for faster heat transfer with building interiors
  - Remains liquid at all times
  - Can be pumped through standard systems integrated into building structures
 
  Considerations:
  - Nanoparticle stability and potential for agglomeration
  - May require surfactants to maintain dispersion

4. Eutectic PCM Mixture:
  Concept: Create a mixture of salts that has a lower melting point than its individual components.
  Composition: Carefully balanced mixture of sodium sulfate, sodium chloride, and possibly other salts.
  Estimated additional cost: $0-$5 per liter
 
  Advantages:
  - Can be designed to remain liquid at room temperature
  - Retains high heat capacity
  - Most cost-effective option for maintaining fluid state
 
  Considerations:
  - May require precise temperature control to prevent crystallization
  - Could potentially separate over time, requiring mixing

Possible mechanical requirements / implementation strategies - obviously the cost is going to be a lot more initially while we bump around to make this work:

1. Circulation System:
  - Design an open-loop (I think this should actually be a closed-loop and I'm thinking wrong due to my exposure to the term in computer system cooling, which I think a lot of folks just have used in my context to mostly mean self built - sorry about the confusion for some who private messaged) system integrated into building structures (walls, attics, under roofs) for direct heat exchange.
  - Use non-insulated, corrosion-resistant piping to maximize heat transfer with the environment.
  - Implement variable flow rates to optimize heat absorption/release based on conditions.
  Estimated cost: $1000-$7000 for a small to medium-sized system...

2. Temperature Regulation Mechanism:
  - Instead of liquefaction, focus on optimizing flow rates and distribution.
  - Use smart valves to direct flow to areas requiring heating or cooling.
  - Implement a predictive control system based on weather forecasts and historical data.
  Estimated additional cost: $500-$2000

3. Refreshing/Regeneration:
  - Design the system with a central reservoir for the PCM fluid.
  - Implement a bypass loop for treatment and rejuvenation of the fluid:
    - Filtration to remove any impurities
    - Potential addition of fresh PCM components to maintain optimal concentration
    - Degassing to remove any absorbed gases that might affect performance
  Estimated additional cost: $300-$2000

4. Monitoring and Control:
  - Install temperature sensors throughout the building and in the PCM system.
  - Implement a control algorithm to manage pumping rates and flow distribution.
  - Integrate with smart home systems for user control and optimization.
  Estimated additional cost: $500-$3000

5. Seasonal Adaptation:
  - For year-round use, consider a dual-loop system with two different PCM fluids optimized for heating and cooling seasons.
  - Use valve controls to switch between loops as needed.
  - Design the system to take advantage of diurnal temperature swings for passive regeneration.
  Estimated additional cost: $1000-$5000

Anyway - I know this is all kinda zany sounding, but I really think there might be some potential. I guess like I said above, we could start small. Maybe make some small aquariums with pumps and try them in various scenarios and then work up?

Kaarina Kreus wrote:So... you need electricity to make this work.
I have none.

Technically I think you could make this without electric, but to do bigger projects it would probably be easier to have some. It might be doable without electric if you make panels and replace them every X cycles (when we figure out if this is months or years or decades)... But I don't see you needing electric if you're using it for clothing and smaller applications, right?

Hmmm... without the table salt, it stays at 95°F, right? And, recharges at anything below that? Soooo... do you think that would work to prevent water from freezing? As in, a wrap made of this stuff, sans salt, and wrapped around a 5gal water supply bucket, for chickens, in the winter? Or am I confusing the science (a distinct possibility!)?

Carla, yes a pcm material could be warmed to melting on a stove or warmed in a solar oven during the day. Then the pcm could for example be wrapped around the bucket and then wrapped with insulation. The pcm would freeze before the water, helping to heat the water.  If you had two pcm’s, then one could be inside warming while the other was in use.

Of course water itself is an excellent pcm. When some of the water freezes it actually releases heat that slows down the rest of the water from freezing.  Unfortunately, the ice caps-off the remaining water, and I’m not sure if there’s any easy way to avoid that without having some mechanical means of stirring or circulating the water.

A pcm near the bottom of the bucket could help provide a small amount of thermal convection.  Actually the tendency for pcm’s to supercool might even be an advantage here. Just as the water surface was about to freeze, the pcm could kick-in, dumping it’s heat with enough temperature difference to convectively circulate the water.

Thanks, Mike! That might *seriously* help with my offgrid troughs & poultry waterer, this winter, when the temps drop down into the 20s and (way) below! That's not a time when I want to risk my hoses & well-house spigot, if I don't have to.

Has anyone tried it?
Does it have limitations?

I worry that carrying another 10 pounds back-and-forth everyday might get tiresome. How would this compare to carrying 1/2 lb of kindling and lighting a dakota fire hole? Or maybe it would be better to use a simple oil lamp perhaps burning home heating oil.

There are so many possible ways….

25-40 watt lightbulb / resistive heater
12v, 2-3.5A
120v 0.2-0.33A
240v 0.1-0.16A

Dakota fire hole or
rocket stove with thermal storage

Charcoal-burning hand warmer

Oil/kerosene/diesel/wax lamp/heater/candle , Zippo hand warmer

Solar thermal

Hot rocks/brick thermal storage in a steel bucket heated on a stove.

Ground-source geothermal
using a heat pipe

Compost heater

Body heat

Solar electric

Non-reusable hand warmer, (rusting iron, salt, activated carbon)

Battery

Frequent water-changes / flowing water

Wind energy

Natural gas / Propane / Biogas

To save on shipping costs, the hydrate-salt-PCMs I see that use commonly available materials (besides water), are: 1) based on calcium chloride, or 2) washing soda.

Both ought to be sealed from the air. Calcium chloride will absorb water vapor.
Washing soda absorbs CO2 (and water vapor and then turns into baking soda).

Washing soda won’t rust/corrode metal; however calcium chloride definitely will.

Other PCMs include wax, and glycerin (a byproduct of making biodiesel).

@Mike can you explain what you're meaning by carrying a 10lb bag every day? Not seeing reason in your remarks so far... Unless you're talking about having some kind of buckets that you transport. I wouldn't take the PCM to temperature differentials, but rather "bring" the differentials to the PCM...

Once frozen, pcm has to be melted again. Same with water. Once frozen, ice has to be melted to get water. Either carry the pcm inside to melt it.  Or heat it outside with solar thermal or fuel.

I’m not sure what you’re saying. Are you suggesting heating water inside, then putting hot water on a frozen pcm?  That would work I think.

Yes, some style of radiator setup and/or pump (probably could do some pretty creative things with the novel gradient opportunities with reducing or eliminating electrical needs even).

Just ordered stuff to do this!
For what it's worth, the seller I picked seems to have interesting taste in things to sell...
ebay.com/str/dudadieselalternativeenergy

I'm all excited! It's been hitting 106 heat index here, I'd love to be able to work longer into the day than I currently can.

Pearl Sutton wrote:Just ordered stuff to do this!
For what it's worth, the seller I picked seems to have interesting taste in things to sell...
ebay.com/str/dudadieselalternativeenergy

I looked at the name, and thought it looked familiar. I recently bought 5 pounds of calcium carbonate from them on amazon, to make more milk paint for my garage remodel. It was not enough, so I just ordered 25 pounds more of calcium carbonate .

Now I'm wondering what other uses there might be for all the extra calcium carbonate I just ordered.... Are there PCMs that use it?

Pearl Sutton wrote:Just ordered stuff to do this!
For what it's worth, the seller I picked seems to have interesting taste in things to sell...
ebay.com/str/dudadieselalternativeenergy

It looks like they have their own website, too https://www.dudadiesel.com/search.php, and specialize in helping people make biodiesel.

The sole owner of Duda Diesel LLC is Brian James Duda. He has a Bachelor degree of Science in Engineering. His studies focused on air-breathing propulsion in aerospace engineering at the University of Alabama in Huntsville.

During his studies in 2005, Brian acquired an old 1986 Detroit Diesel All American Bluebird bus in his home state of Massachusetts. After driving it for a few weeks, he found the high fuel price for diesel fuel of $3.00/gallon to be too much, and explored the alternative fuel of vegetable oil. In the process of finding, filtering and using the fuel, he found that it was very difficult to obtain a lot of the expensive supplies needed for treating waste vegetable oil and the chemicals needed to make biodiesel. He then created a small online store which carried all of the basic supplies for filtering vegetable oil & then for processing biodiesel. As the business increased, he then pushed to create an online store dedicated to all alternative energy supplies for do-it-yourselfers and other small businesses. Duda Diesel now offers many supplies for SVO, biodiesel, solar water heater technology and will soon also push for solar electrical cells (PV cells), wind power, geothermal systems and energy efficient devices such as LED lights and systems which recycle heat.

Duda Diesel strives for excellent customer service and speedy shipping times while delivering quality products at a reasonable price. The goal of the company is to stay American owned and operated and to bring jobs back to the American economy. Ultimately, Duda Diesel would like to design and manufacturer its own products for sale domestically and internationally.

It seems like a nice company to support. I know their calcium carbonate, at least, is a great deal and seems high quality!

One my favorite reactions is to bake in the oven a thin layer of baking soda (NaHCO3) at 300 deg.F (150 C)  or hotter for the better part of an hour. It emits H2O and CO2 and turns into washing soda (Na2CO3).  

Na2CO3.10H2O is a pcm.

Also a lot of times I find gypsum drywall (CaSO4.2H2O) in the trash.  

Na2CO3 and CaSO4 react in water to make Na2SO4 (the pcm mentioned above and in NHIT’s video), and CaCO3 precipitate!  

I do know this reaction works well, is easy, and about as safe and non-toxic as chemistry gets. I’m not entirely sure if drywall as a source of CaSO4 is pure enough. Maybe the glue and paper should be washed out first to get a more pure Na2SO4 pcm product. Or maybe the product could be purified with crystallization if needed.

Despite Ben’s video making a compelling case for measuring the melting point of his PCM at 18 deg.C, I remain skeptical because: 1) In general, diluting a mixture changes its melting point. 2) It might not make sense to assume that the PCM freezes uniformly (or “congruently”).  3) The raw PCM might have limited thermal conductivity. (Some research adds components like graphite in order to increase thermal conductivity).  4) Ben’s recipe departs somewhat from other literature. Also, even in the literature, reported melting points vary by easily +/- 1-2 deg C. (I don’t doubt Ben’s PCM works, I’m just holding out for confirmation on the melting point.)

I could see dissolving the salts separately in hot water and *then* mixing them together. But the peak solubility for the *mixed* salts is around 22.5 deg.C.  So to make a salt solution that is saturated near room temperature, heating the mixture to boiling might not help so much.

So, I tried to find an original source in the literature for the “18 deg.C” claim, and then I tried to calculate the recipe quantities from that…

Multiple possible “recipes” / ideas / notes dump below…. (Also ideas for optional gels/thickeners)

Note: Use weights (not volumes) if possible for better accuracy.

———
reported mp 18 deg.C source:

https://www.eng.mie-u.ac.jp/research/activities/29/29_31.pdf


240 cc * 1.4 g/cc = 336 g anhydrous Na2SO4
(37 % of total mass)
336 g anhydrous Na2SO4 / 142.04 g/mol = 2.37 mol anhydrous Na2SO4.

119 cc * 1.3 g/cc = 154.4 g NaCl
( 17 % of total mass)

154 g NaCl / 58.443 g/mol = 2.64 mol

418 cc * 1 g/cc = 418 g H2O
(46 % of total mass)

908 g total mass

———

mp 4 deg.C

240 cc * 1.4 g/cc = 336 g anhydrous Na2SO4
(31 % of total mass)
336 g anhydrous Na2SO4 / 142.04 g/mol = 2.37 mol anhydrous Na2SO4.

108.5 cc * 1.3 g/cc = 141 g NaCl
( 13 % of total mass)
141 g NaCl / 58.443 g/mol = 2.41 mol

157 cc * 1.1 g/cc = 173 g KCl
173 g KCl / 74.555 g/mol = 2.32 mol
(16% of total mass)

434 g H2O
(40 % of total mass)

1084 g total mass



————
With Borax for nucleation

est. mp 18 deg.C

sodium tetraborate decahydrate (Borax) 4% wt.

~240 cc * 1.4 g/cc = 336 g anhydrous Na2SO4
(35.7% of total mass)
336 g anhydrous Na2SO4 / 142.04 g/mol = 2.37 mol anhydrous Na2SO4.

~118 cc * 1.3 g/cc = 153 g NaCl
( 16.3% of total mass)
153 g NaCl / 58.443 g/mol = 2.62 mol

414 cc * 1 g/cc = 414 g H2O
(44% of total mass)

941 g total mass

———

With Borax for nucleation

est. mp 4 deg.C

sodium tetraborate decahydrate (Borax) 4% wt.


240 cc * 1.4 g/cc = 336 g anhydrous Na2SO4
(29.8% of total mass)
336 g anhydrous Na2SO4 / 142.04 g/mol = 2.37 mol anhydrous Na2SO4.

~108 cc * 1.3 g/cc = 141 g NaCl
( 12.5% of total mass)
g NaCl / 58.443 g/mol = 2.41 mol

~158 cc * 1.1 g/cc = 174 g KCl
174 g KCl / 74.555 g/mol =  2.33 mol
(15.4% of total mass)

433 cc * 1 g/cc = 433 g H2O
433 g H2O / 18 g/mol = 24 mol
(38.4 % of total mass)

1128 g total mass


——
Borax “Slime”

STEP 1:
dissolve 1/4-1/2 teaspoon of Borax (more is firmer) in 1/2 cup of warm water and set it aside. (Use only 1/4 teaspoon of Borax if using clear glue)

STEP 2: In the second bowl,
add 1/2 cup pva white glue or clear glue. Add 1/2 cup water to the glue.

food coloring optional. Mix.

STEP 3: Pour the borax/water mixture into the glue/water mixture and stir.

STEP 4: Spend a few minutes kneading the mixture together. You may have leftover borax solution.
Knead and play with your slime until smooth and stretchy!


———

Liquid starch slime or saline solution slime {although they contain boron-compounds too} will leave you with a more cloudy clear slime instead unless you add food coloring.

The saline solution is the slime activator and helps the slime to get its rubbery texture! Be careful; adding too much saline solution can make for a slime that’s too stiff and not stretchy!

——
Slime Putty

* 1/4 teaspoon Borax Powder
* 1/4 cup PVA White School Glue
* 1/4 cup warm water
* Food Coloring

Stir it up! At first your putty will look kind of lumpy and stringy!
knead 1-2 min until  smooth


——-

solubility of Na2SO4 always increases with decreasing NaCl concentration at T = (313.15 to 373.15) K

——-
Polyacrylamide (PAM) was proposed as the thickener  3-5 wt.%
sodium tetraborate decahydrate (Borax) 3-5 wt.%
was proposed as the nucleating agent, and expanded graphite (EG) was proposed as the high thermal conductivity medium. 0-3 wt%

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267564/

Ha, Pearl! Too funny - I ordered mine today, too!

Carla Burke wrote:Ha, Pearl! Too funny - I ordered mine today, too!

Waiting with baited breath for both of you to report your results!

My big question is whether it releases the energy over enough time to be useful at keeping temperature "steady", rather than spike and crash. I totally believe it could be a useful tool in an "emergency kit" when someone's out somewhere and either they, or someone else, is having heat stroke. But will it help an individual stay cool while working for an hour or 4 hours without them constantly having to swap them out with fresh ones.

If I can buy John even one or two more hours a day, so he can be outside, like he wants to be, doing what he wants to do - it will all be worth it. Especially so, since I can make both wearable stuff and recovery items. I'm thinking helmet & vest inserts, for a safer, longer motorcycle ride, an extra hour on the forge, taking care of the farm... Even just ways to help him not worry that he is literally going to die, doing necessary stuff, much less fun stuff...

Y’all must have used ice packs before, with a layer of cloth between it and your skin so the temperature isn’t so cold. It’s the same as that. Literally an ice pack is a PCM.

Mike Philips wrote:Y’all must have used ice packs before, with a layer of cloth between it and your skin so the temperature isn’t so cold. It’s the same as that. Literally an ice pack is a PCM.

I've used covered ice packs on injuries as first aid, but I don't have enough body fat to use it for this sort of hot weather management. If the weather is really hot, I'm not sure I'd even tolerate a PCM that changed at 18-20C like I believe pure glycerol is supposed to do.

So yes, plain water is a PCM that gives off the most energy right around 0C. We use it as a thick brine with table salt to fast freeze meat chickens when we've done a lot of processing and we don't want to give our freezer a hernia - the brine bottles thaw, freezing the meat, then over the following week, the brine slowly re-freezes. It really is amazing watching the process and is much safer than the meat having to freeze based solely on how fast the freezer can do the job.

Mike Philips wrote:Y’all must have used ice packs before, with a layer of cloth between it and your skin so the temperature isn’t so cold. It’s the same as that. Literally an ice pack is a PCM.

Yes, it is. But, in temps of 90° - 100°+, draped on a hot human body  especially with the sun beating down, ice is simply not practical to try to wear, while working/playing, and must be dropped to below freezing temps to recharge. Few would be able to even cycle panels out of their freezers, that would be sufficient to cool a human torso, much less a building - even a small one. I'm personally not terribly concerned if the measurable temps are off by a few degrees, if the items can be recharged, simply by bringing them into the air conditioned house our tucking them into a cooler, for a little while.

Carla Burke wrote:... if the items can be recharged, simply by bringing them into the air conditioned house our tucking them into a cooler, for a little while.

Even if you need to put them in the fridge to fully re-charge (ie, *all* of the material has changed phase), that's still a win when your goal is to help a body cope with 90F weather or higher. As you pointed out, if it gives people 1 hour longer to get jobs done they need or want to get done, it's a win.

But there is a cost - water is heavy. Not sure how heavy these PCM packs will end up being. For people who weigh upwards of 150lbs, they may not notice suddenly added 10 lbs to their gear, but I certainly will. Good thing that I live somewhere that hopefully won't require daily use of such things. But we do occasionally have exceptional weather that may not seem "hot" by Southern USA standards, but our bodies aren't used to it, so they haven't adapted.  

The cooling per unit weight is best for ice 333 kJ/kg.  sodium sulfate chloride hydrate is 286.  The recipe in Ben’s video will be less because he diluted it with additional water.

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My quick attempt to model a proof-of-concept…

Google says:
Normal human skin temperature on the trunk of the body varies between 33 and 37 °C (92 and 98 °F), though the skin's temperature is lower over protruding parts, like the nose, and higher over muscles and active organs.

Wikipedia says:
Research on human tolerance to cold has shown that onset of [skin-too-cold] pain occurs at 15°C (59°F) skin temperature (Havenith et al. [10]), numbness occurs at 7°C (44.6°F) (Provins and Morton [11]) and risk of frostbite is risked at 0°C.
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My calculations:
Suppose temp of skin 20-30 °C.
Suppose Ice PCM:  0°C.
Delta-T = 20-30 °C

Ice cooling capacity: 92.5 Wh(th)/kg

Suppose Goal: 100-200 watts cooling

Suppose PCM dimensions:
15-25cm H , 60-90 cm L.
(wrapped around abdomen)

Area = 900 - 2250 cm2
Suppose pcm 1 cm thick

Vol = 900 - 2250 cm3
Mass = 0.9 - 2.25 kg
Cooling: 300 - 750 kJ
Duration: 3- 3.75 hrs.

heat flux:
100W / 0.09 m2 = 1100 W/m2
200W / 0.225 m2 = 890 W/m2

Insulation pcm-to-skin:
R-0.1 (°F⋅ft2⋅h/BTU )
= ( 0.0175 °C⋅m2/W)
(Delta-T) 20°C  / ( 0.0175 °C⋅m^2/W) = 1140 W/m^2 heat flux

Suppose average R-3/inch insulation
Insulation thickness = 0.033 inch (0.85 mm)

R-0.19 (°F⋅ft2⋅h/BTU )
= ( 0.033 °C⋅m2/W)
30°C  / (0.033 °C⋅m^2/W) =
910 W/m^2

est. Insulation thickness = 0.063 inch ( 1/16 ”) (1.6 mm)

Threshold case: Cooling power at 15°C (59°F) skin temp (onset of skin-too-cold.):
15°C / (0.033 °C⋅m^2/W) *0.225 m2=
102 W.

Estimate approximately 2:1 ratio between cooling-power goal and onset of skin-too-cold.