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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.


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.


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.


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


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.


Comments (291)

VickiS said:
VickiS's picture

If it's a heat pack that you've already used, it could be rice. I made my own heat packs with rice some time ago and have just had a hole appear in one from being loved way too much, and the rice inside now resembles small white granuals. I have been making rice packs for myself for years and love them.

Judy Kay said:
Judy Kay's picture

I just took an old heat wrap apart and it had some kind of tiny white granuels in it, looks about the size of bird food or smaller. Does anyone have any idea what they can be and where I could find them. I want to make some for Christmas gifts.  All the information I have read has been extremely helpful and I want to send a big huge THANKS to everyone who has posted ideas and information.

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

@Judy - It's hard to tell, but it sounds like something that isn't an organic filler. We didn't test any non-organic heating beads. Perhaps someone else in our visitor universe may recognize what you've described. 

Maya Tasa said:
Maya Tasa's picture

Hi. I love the idea of making a heat pack myself. Can i use a used cotton t-shirt,cut to size, for this? 

Toi said:
Toi's picture

hi, has anyone ever used


Hi, has anyone tried beach variety sand to fill bags instead of rice?

Shahalpa said:
Shahalpa's picture

I think sand heats up very quickly , so careful of being burnt

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

@Toi -- we have not had anyone test that. You could certainly do a test just as we show above. Sand will present several challenges; 1) it is so fine, it will be hard to keep it from leaking out through the seams -- even with a super tight stitch, 2) it is likely to be rather heavy, 3) I really don't know how well it would retain the heat... but as mentioned, the test style above would work well. Let us know what you find out.

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

@Maya -- we did not test with a cotton knit, but can't think of any reason why it wouldn't work. Look for 100% cotton and a faily thick knit - you wouldn't want a thin t-shirt material. If possible (as we always suggest), make a small version and test it.

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

@Cheryl - Yes, you can use brown rice. Your heating times may vary - so test first.

Laurie Levell said:
Laurie Levell's picture

I have quite a few bags with different fillers that I have made and received as gifts because I suffer from migraines.  The bags I use for the freezer have deer corn or popcorn in them.  I personally think the popcorn is more comfortable than the deer corn as I place it behind my neck when I lay down.  Since I only use the popcorn bags for freezer use I don't worry it will pop!  I have made flaxseed bags but find the smell overpowering when I warm them as I am super sensitive to smell and odors when having a migraine.  I find the long cooking rice to be best for warming bags.  Ideally I would LOVE to find a filler that has NO odor.  Any suggestions?

1970Lorrie said:
1970Lorrie's picture

You can add a few granules of charcoal that is found in the fish tank filter system section of WalMart or any pet store. It works great and is ok with the heat 

Meganmoni said:
Meganmoni's picture

I also surrfer migrains, the only smell I can take is peppermint.  I rub it on my temples, you might try adding that to the flaxseed and see if it helps.  But I would go somewhere where you can test the smells.  Not all mints are the same!  GL

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

@Laurie - It sounds like you've experimented with a LOT of options. With your specific sensitivities, I can't really think of an organic filler with zero odor. Perhaps our helpful visitors have some additional thoughts on alternative fillers that we have not worked with. 

Missdebs said:
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What  about how they work cold? Which product is best to fill with to remain cold the longest. 

anne.adams said:
anne.adams's picture

@Missdebs: We didn't experiment with cold, but there are few comments from other uses about cold. We may do this test in the future.

KP said:
KP 's picture

I want to make a few but using essential oil.  But don't know how it would hold up to being mw a few times without breaking down the rice or flaxseeds 

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

@KP - You need just a few drops of essential oil, a little goes a long way with the concentrated oils, so there really wouldn't be enough to negatively effect the rice or flaxseed.

Kelly Anderson said:
Kelly Anderson's picture

I have mixed Lavender and Eucalyptus, in my rice , and didn't get any com a in ts, from my return customer..

Gloria Friesen said:
Gloria Friesen's picture

I have made many microwave bags filled with brown lentils. I find them in the bulk section. The odor is mild and not unpleasant. They retain the heat well. Recently I made some bags with flax seed. I like the way the bags feel but I find they do not retain the heat as long as the brown lentils.

Alicem said:
Alicem's picture

THANK YOU !  was looking for this kind of information.

Thank you, Liz (editor)! Thank you for publishing this web page!

thanks to all the contributors also.  This is one place where the WWW excels! Where peopl can share their personal experiences..practical. Excellent.


tha ks again


Liz Johnson.Editor.Sew4Home said:
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@Alicem - Glad you found us - we hope you'll come back often - and bring all your friends 

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


Liz Johnson.Editor.Sew4Home said:
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@ 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.

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.

shahalpa said:
shahalpa's picture

When i bought wheat bags, label said, every 5th time u warm up, put a bowl or glass of water  alongside the wheat bag, to retain the moisture, prevent from cracking up the wheat

Simply Margie said:
Simply Margie's picture

I usually make my heat packs with a combination of rice & flax seed... 50/50, but I have just started using the same combination of rice & flax seed, but more like 90% flax seed/10% rice... they last longer.

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

Liz Johnson.Editor.Sew4Home said:
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@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. 


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