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Organic Fillers For Warming Pads: We Compare Rice, Corn and Flaxseed

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Microwavable heating pads with organic fillers are a wonderful way to soothe sore muscles or just warm up on a cold day. Their combination of toasty warmth and good smell are a natural remedy you can enjoy every day without side effects. The warming pad project we did here at Sew4Home is one of the most popular gift items ever featured. Most likely, it's because they're not only functional, they're also really easy to make. Everybody who makes them seems to have a favorite filler. So we thought we'd do a little testing to see if we could find out which one is best.

Cotton on the outside, but what should go inside?

You can use other substrates, our original pad project featured fleece and cotton ticking, but the traditional choice for anything microwaveable is 100% cotton. It can get very warm without melting and has a nice feel against your skin. Of course, like anything you put in the microwave, even cotton will eventually burn if you cook it too long. The benefit to using the organic fillers is they require very little time to heat thoroughly, fifteen to thirty seconds is usually plenty. 

But what about the filler? What should you put inside your heating pad to get the best results? 

First of all, you want your filler material to be microwaveable; that eliminates anything with a metallic component, which will spark. It should stay warm for an extended period of time. It should have a nice smell or no odor when heated. And finally, it should have a nice feel against your skin. This last reason is probably why neck warmers filled with driveway gravel never caught on.

Talking with our Sew4Home team and then looking at what's recommended on the web, we found a number of different fillers people have tried. The more exotic range from silica beads to cherry pits. But the ones that appear to be the most popular (and in our experience the most practical) are: rice, dried corn, and flaxseed.

    

All three meet the requirements of retaining heat, having a pleasant smell, and feeling good against your skin. Additionally, we like the fact you can buy any of these very inexpensively in the bulk food section at most supermarkets. If you're making more than a few heating pads, this is something to consider.

We wanted to know which of our three finalists – rice, dried corn, and flaxseed – would perform best in a highly scientific test.

Which heating pad filler is best? Our scientific analysis.

To test our fillers we made three 5½" x 5½" test pads from scrap cotton fabric and filled each with 1½ cups of the various fillers. 

We chose to compare them by volume rather than weight because that's the limitation on your sewn warming pad.

Heat retention

Using a 1.65 kilowatt microwave, we heated each of the pads for thirty seconds. Using a food thermometer, we measured how warm the pad was right when we took it out. And then how warm it was after sitting out for five minutes. 

As a reference, we heated a cup of water to 140° and found it had cooled to 124° in five minutes.

Rice: 140° out of the microwave. Five minutes later had cooled to 136°.

Dried Corn: 158° out of the microwave. Five minutes later had cooled to 142°.

Flaxseed: 144° out of the microwave. Five minutes later had cooled to 142°. This one retained the most amount of heat.

Smell

We'd heard some people complain that grains, like the rice and corn, can have a cooked smell when heated. We didn't detect any strong smell. But cooking odors may be caused when the grains are microwaved too long and burn a little. 

Flaxseed is a seed and so much less prone to cook. However, of the three, the flaxseed actually had the most noticeable smell.

Feel

This is the most subjective test. It really depends on the texture you like on your skin.

Rice: This has a nice "full" feel, almost like a batting fiber.

Dried Corn: It has a granular, pebble feel that's pleasant when resting on your arm or neck.

Flaxseed: This flowed the most easily and conformed to where you laid it.

Cost

As mentioned above, we narrowed it down to our three finalists because they were so readily available from the majority of supermarkets with bulk bins. All were well under $1.00 per pound.

Rice: $.53 per pound

Dried Corn: $.96 per pound

Flaxseed: $.83 per pound

Conclusion

If you're going solely for heat retention, use flaxseed. But all three of the fillers we tested performed better than water and so would stay warm longer than a traditional hot water bottle. For smell and feel, we found things to like about all three. 

We now expect the major scientific journals to begin clamoring for the publishing rights to our detailed research, but you can use it for free.

Conduct your own experiment

Put on your white lab coat and do some testing of your own.

Make a few of our Microwaveable Rice Heating Pads and give each one a different filler. Ask your family and friends to tell you which one they like best. Then leave us a comment about what you found out.

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Comments (261)

naturegirl said:
naturegirl's picture

This is awesome, thank you!! ...and I love your whimsical sense of humor coming through the text. You crack me up!! 

Thanx!!

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ naturegirl - So glad you found the info helpful.... yes, gotta keep smiling, right?!

fluffycat34 said:
fluffycat34's picture

I bought a bag in Phoenix that had ground lava rock in it worked well for mom who has allergies. But don't know where to buy it. 

RoseRosannaDana said:
RoseRosannaDana's picture

you can buy lava rock at a landscaping place, but it isn't ground. I don't know how hard it would be to crush it yourself.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ fluffycat34 - that is not something we've worked with, but it sounds like it might be something that could also be used in an aquarium or a reptile environment. Maybe you could try a pet store. 

Pat DeNoble said:
Pat DeNoble's picture

I read that cotton thread needs to be used for these warmers. Would cotton covered polyester work without burning/melting in the microwave? Thanks.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Pat - Cotton is usually the top choice for warmers. We have used that most often. Although, we also used a cotton in combination with a polyester fleece in our original rice pads tutorial with good results (link below). You, of course, don't want anything with metallic threads. And, no matter what you use, don't overheat - these types of heating pads are traditionally meant to be heated for just a few minutes.

http://www.sew4home.com/projects/pillows-cushions/microwavable-rice-heat...

Refugio said:
Refugio's picture

I'm wondering if brown rice would make a good heating pad. Have you tried using brown rice?

Will it have a stronger smell than white rice?

I've made heating pads with white rice, but the rice tends to get brown and falls apart after multiple heating in MW, so need to make new ones now.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Refugio - We did not specifically test any options other than those shown above in the article. There are definitely a lot of opinions within our comments here as folks have weighed in with their personal experiences. In theory, brown rice should perform similarly to the white rice. The smell is an unknown - and is also a personal preference as to whether it smells good or bad. As noted in several answers below, we often suggest making a small prototype bag to test your filler choice. 

snowbird4 said:
snowbird4's picture

It shows whole corn in the picture but grits in the list, which is it?

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@snowbird4 - Hmmmm _ I wonder if you're seeing a cached version of the page. We tested whole corn, which is what is shown in the list. Sorry for any confusion. If you re-load, you should see the latest version of the page.

Dee Sz said:
Dee Sz's picture

I made a few of these for the family and we love them except that they are coming out of the microwave a little moist. Enough moisture that I have had to wrap them in a towel to use. The one I made with fleece only emits more moisture than the one I made with half fleece and half cotton. Any suggestions?

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Dee SZ - We're not sure what pattern you used or the size, length of time in the micro, etc -- so there are a number of variables, but since the fleece is non-organic, it is likely trapping whatever moisture is occuring. You may want to stick with all cotton. 

clsbauer42 said:
clsbauer42's picture

Can you make these with fleece fabric or do you recommend cotton?  I tried making fleece hand warmers with rice and they stunk after I microwaved them.

catm said:
catm's picture

I am a little confused. Is there an outer layer of fabric and an inner layer, or would just one piece of fabric suffice? Would cotton flannel or cotton towelling work if you only use one layer?  Also how much rice would it take to fill a tube 4" in diameter and 30" long?

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@carm - This article simply compares the various filler options. We do have our own actual rice pad tutorial, which I've linked to below, which may be helpful. There are many other options online and, as shown by the numerous comments people, it's really a matter of personal preference regarding construction as to whether an outer sleeve is necessary. In general cotton fabrics are your best option for the pads. You would need to deterine your own amount of filler; our pads used about 6 cups of rice each. 

http://www.sew4home.com/projects/pillows-cushions/microwavable-rice-heat...

Ss121978@yahoo.com said:
Ss121978@yahoo.com's picture

i did a mix of rice and flax seed adding a lavender and sandalwood combination essential oil to the mix and they are wonderful.  They mold nicely to the body part, hold heat for up to thirty minutes.  So far I've made the knock wraps and eye pillows.  I am about to tackle a full back pad.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Ss121978 - Thanks for letting us know this combo worked best for you! It's our fave too.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Bunkhouse - So sorry, but we did not test any beans as we didn't have them on our original list of likely candidates. There are lots of great comments here - and it seems to me there have been some folks who've mentioned their experiences with various beans (including coffee beans) - give a scroll through and see if you find something. If not, perhaps someone else will weigh in with their test results. 

Rebecca Mahon said:
Rebecca Mahon's picture

I'm making neck/shoulder warmers, was wondering what to fill it with that would not be to heavy, yet heavy enough to help ease sore muscles, and that would last longer and not have such a distinct smell. Thanks. 

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Rebecca - We've had the most luck with rice - I've linked to our microwaveable rice pads tutorial below. Often, as you can see by the many comments below, it's simply a matter of persaonl preference. There may be non-organic fillers that could last longer but we have not used or tested any of those. 

Kirsten W said:
Kirsten W's picture

I recently conducted a similar test, but i also used quinoa, barley, beans, and coffee. Quinoa undoubtably smelt the WORST!  I rate flax seed as 1 overall. My heat pack is rice and i didnt notice the grain smell until 2 weeks of use. I mask that burnt scent with essential oils. I also found the flax seed on amazon for .18 cents an once. 

Heather Rogers said:
Heather Rogers's picture

Kirsten~ how did the barley come out?  I'm curious as I just filled one but haven't sewn it up yet...

Rut Carla said:
Rut Carla's picture

You deem to tell me that you've conducted a similar test but you've used coffee beans? I've been looking around seeing if coffee is a good candidate, (which is how I got to this website). So what have you found? Do the coffee beans have a good smell? Good texture? Would you recommend it? Thank you.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Kirsten - Thanks so much for sharing your results!

Miss K said:
Miss K's picture

I was curious is to which of the 3 will work well as a hot or cold pack? Do you recommend anything if none of the three can be used ias hot or cold.

Shannon 55 said:
Shannon 55's picture

I have put my rice pack in a wal-mart sack and then in the freezer for a few hours or over night it worked great for a cold pack.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Miss K - We didn't test for cold -- only heat, so we can't give you a recommendation. However, there is nothing inherently wrong with freezing any of the substances, other than the possibility of retained mositure, which means putting the pad in a sealed plastic bag before putting it in the freezer would be a good idea. Your best bet would actually be to do you own little test - as we did for heating. If you do, please let us know your outcome. 

Valerie Robinson said:
Valerie Robinson's picture

I use frozen peas. I just mark the package ice pack. The peas conform to any body part and stays cold for a good 30-40 minutes and can be re-frozen many months. 

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Valerie - Frozen peas are a classic solution!

Penny123 said:
Penny123's picture

Would it be ok to use roasted flax seed for these hot packs ?

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Penny123 - Sorry, that is something we didn't test. You might want to do your own little test to see if the roasting (which breaks down the outer shell) affects its ability to retain heat. You'd also want to make sure it is still super dry. You don't want any oily residue. 

Cora said:
Cora's picture

Can you recommend which of the three is the most lightweight for travel? I'm going to guess corn, but I'm not sure! 

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Cora - Well, there's a new question  - we did not test any of them for weight and we currently don't have all of them on hand to confirm. I would say agree that corn is probably a bit lighter than rice or flax seed. If you can find them all in one place as we did (bulk food section of our local natural foods store), you could simply way a cup of each on their scale. 

shirleycollins said:
shirleycollins's picture

We made our first bags in 2002, in a class in a quilt shop. feeder corn and no bugs. I still have one of my original bags and use it at least 3 times a month( more depending on muscle injuries). Then we made a batch 8 years ago for Christmas gifts for the whole family, no bugs...corn from grain store. Now I bought 40 lbs yesterday from a hardware store to make bags in my before school program ( gifts for parents ) Hopefully no bugs. But I do believe I will freeze it just in case. I am feeling scared. I will comment again. Also we use 100% cotton for inner and outer shell and thread. holds up like crazy!!!

RoseRosannaDana said:
RoseRosannaDana's picture

I have used feeder corn for abour 30 years now And never had any bugs. Before I gave them as gifts, I microwaved them a couple times to reduce the moisture content. We are still using the same bags from 30 years ago.  

Lewis said:
Lewis's picture

Just a quick advice and warning: Grain filled heat pads can catch fire in the microwave or even outside, when it gets in contact with flamable materials. Therefore be very careful with the time you set for heating, and never leave it unnatended. 

Heidi E. said:
Heidi E.'s picture

I used barley the first time I make these and that worked well also.  My family tends to over-heat them, so they did smell (and even scorched the fabric after a while) but they still worked.  I'm just replacing them now after more than 10 years.  I think I might try flax this time.

Krista said:
Krista's picture

"Do you have any alternative suggestions to heat the pad without using the microwave? 

We received a rice pack once that gave instructionsome for heating in the oven. The fabric does tend to singe easier. This could also be that these rice bags were years old already before using them I in the oven to begin with. Either way ,  directions for heating in a conventional oven: heat for 15-25 min at low heat between 200-300 degree. Heat in a glass baking dish large enough to spread out the pack a little bit.inside the dish. Heat for 15-25 min. I have noticed that the packs do not hold as much heat initially, but if you use it for a few 10-20min and then put it back in the oven for 10 min of so, it will then come out able to retain heat for at least 30min. I have also noticed that they warm up more evenly when I ensure that there is a small dish of water in the oven at the same time the bags are warning up to help not dry out. 

Kendra george said:
Kendra george 's picture

we have always used rice for years and it works great. My friend gave me a corn one for Christmas last year and it keeps heat very well but my husband hates the smell. Does the flaxseed have a strong smell?

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@Kendra - as mentioned above, the flaxseed does have the most distinct smell -- kind of nutty. You might want to purchase a small amount and just make a little sample bag to test the heat retention and smell for yourself. People really vary regarding what they think is a strong smell. 

Terra said:
Terra's picture

Kendra for all those worried about critters in your fillers, simply place your fillers in the freezer for at least 24 hours kills the larva and critter in any of your fillers.

Ariana said:
Ariana's picture

Thank you so much for posting this because I was wondering about this for about a week.

Elaine R. Xero said:
Elaine R. Xero's picture

So how can you tell the difference between popcorn and corn you can heat up? How does it not pop like pop corn? 

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Elaine - you can Google it for even more detils but basically, the two are different varieties and grown separately from each other - sweet corn is harvested when tender, popcorn when the plant is brown. Unlike regular corn, popcorn hulls are non-porus to trap steam. They explode and turn inside out. Regular corn may pop at very high heat, but not consistently and it’s not big and and fluffy like popcorn.

Liz Johnson.Editor.Sew4Home said:
Liz Johnson.Editor.Sew4Home's picture

@ Lily - So sorry but that is not something we've tested. I don't know how, if at all, they would retain heat since they are so fine. If you have some on hand, you could try a test of your own in your microwave to see how they perform. Let us know your results.

JessicaT said:
JessicaT's picture

Recently I've been making lavendar pillows with chia seeds as the fine seeds conform very nicely to the face for an eye pillow! The chia seeds do not retain heat as long as rice or flax seeds - but I find them much more comfortable, which is worth it to me! Just keep in mind chia seeds tend to be more expensive than the other options. Someone left me some chia seeds when they moved away, so I didn't mind experimenting! 

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