Fabric Testing - Insert Absorbency

Fabric Testing: Complete Results and Conclusions

My first conclusion is that this test took WAAAAY longer than I expected it to!  Now if I were a real scientist I would start out by explaining my expectations and the questions I hoped to answer, then my methodology etc etc (boooorrrring!) so instead I'm going to skip straight to what I learned (shhh don't tell my PhD parents!) feel free to scroll down to view all the nitty gritty results, how I got them, and a close up of all the fabrics I tested so you see the visual differences between them.

Conclusion 1: ZORB WINS!  (in compression testing)

As I was testing the inserts, I noticed that absorbency doesn't really matter unless the fabric can HOLD ON to what it absorbed.  I allowed each insert to drip for 30 seconds prior to weighing but even after that I still wouldn't want anything that sopping wet on my baby's bum.  Instead what I cared most about was how the fabric preformed under moderate pressure (15 lbs to be exact) this isn't a lot of pressure and even after each fabric was squished under 15 lbs, there was a LOT of water that I could easily squeeze out with my hands.  The purpose was not to put extreme force on the insert but to see how it would hold water under the weight of an average baby.  In compression testing, Zorb won, hands down!

Conclusion 2: ZORB WINS AGAIN! (in compression/thickness testing)

Not only was I looking for something that would preform well under moderate compression but I also wanted something that would preform well based on thickness so after I got all of my absorption results, I divided by thickness to get how much a 1" thick insert, made of many layers of a particular fabric would hold.  Zorb won again showing that even though the fabric is quite thick, when you correct for thickness it STILL holds more than any other fabric we tested.

Conclusion 3: Zorb/Microfiber wins, and no Zorb did NOT sponsor this test lol! (in cost)

I haven't gathered all the official costs of all the materials yet but Zorb and Microfiber both absorbed the most per layer as well as per inch thick.  Oddly, they are also both the cheapest fabrics we tested.  Considering they were also the thickest fabrics we tested its safe to say they were ALSO the cheapest per inch thick.  I'm not sure which is cheaper, probably microfiber since you can get it anywhere whereas Zorb is only made by Wazoodle but I'll have to run the numbers to find out for sure. 

Conclusion 4: There IS room for 2nd place and Hemp (or bamboo) French Terry has it! (In compression/inch thick)

I'll let you scroll down and review the full results yourself to make your own conclusions but MANY moms prefer only all natural fibers, not to mention Zorb CANNOT be used on its own, its a non-woven fabric that needs to be encased in something so if you do use Zorb you will NEED another fabric to sew around it.  This means that there is a clear NEED for a second place winner.  Although the results point to microfiber being the next best absorbent layer next to Zorb, I wanted to give the 2nd place spot to a natural fiber since many babies do not tolerate Microfiber well.  French Terry is CLEARLY that second winner, absorbing about 1.5 ounces more per inch thick than the next best fabric.  

Now why did I say hemp OR bamboo french terry gets 2nd place when I didn't TEST bamboo french terry?  Well I did test hemp and bamboo fleece and results show that they absorb similarly (bamboo tended to absorb a little more but the bamboo/hemp blend actually absorbed the most of the fleeces) this tells me that the WEAVE of the fabric actually has more to do with absorption than the MATERIAL the fabric is made of.  Therefore the french terry in either bamboo or hemp should also absorb similarly.  Personally I would go with a bamboo french terry since its cheaper, requires less prep, and is softer!

That's it for my quick and simple conclusions, now the...

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FULL RESULTS!

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Complete data is available via this link, I have summarize the "result highlights" below. 

All weights are in ounces, all thicknesses are in inches.  For comparison an average baby pees (in ounces) age*2+2 so a 2 year old has a bladder capacity of 2*2+2 or 6 ounces.  A 1 year old would have the capacity of be 1*2+2 or 4 ounces.  The chart below will tell you how many ounces an insert made of a particular fabric type will absorb, if the insert was made of enough layers to make it 1 inch thick.  A 1" thick layer of Organic Hemp Fleece, for instance, would absorb 25.76 ounces in 30 seconds.  Although my ounces are measured by weight, they are a rough equivalent for fluid ounces (technically 1 ounce of water weights 1.043 fluid ounces).

Below is a summary chart of the data.  To the left of the red line shows absorbency per layer of fabric, data to the right of the red line shows absorbency if all inserts were 1" thick (basically this means I corrected for thickness).

Below is a graph showing absorbency per layer, fabric types are sorted by compression absorbency per layer. (sorted by the GREEN bar)

Below is a graph showing absorbency per layer per inch thick, fabric types are sorted by compression absorbency per layer per inch thick. (sorted by the GREEN bar)

There is one other conclusion I'd like to add, when you look at the chart above you will notice that while there are distinct differences in absorption per inch thick, they are roughly within 20% of each other.  Every fabric I tested absorbed pretty well and honestly I'd be happy to use any of these fabrics in my inserts. The main difference is cost, those that were thin to begin with would require you to purchase a LOT more layers to achieve the same absorbency of those that were thicker.  Also the natural fibers tend to cost quite a bit more but apparently don't absorb any better.  That being said, if someone handed me a stack of free organic hemp fleece inserts, I'd absolutely use them in a heartbeat even though they "technically" got last place - they still absorb pretty darn well!

Methodology

(1) Acquire a variety of fabrics commonly used for cloth diaper inserts.  Emphasis was placed on getting several materials as well as several fabric weaves so that comparison's could be made not just based on material type but also the way the material was assembled into a fabric.  For instance we wanted to be able to compare a hemp fleece to a bamboo fleece but we also wanted to compare a bamboo fleece to a bamboo velour to see what type of difference the fabric weave could make.  We bought all materials from https://kidsinthegarden.com for approx $35 including shipping.  The service was fantastic and we saved a good amount of money through buying fabrics by the inch instead of the yard as well as misc scrap fabric. 

(2) Prep fabrics.  I prepped the fabrics by washing and drying them all together 8 times.  The first time I washed with the normal amount of soap (Planet brand) and 1 tbsp of oxyclean.  The purpose was to use the enzymes in the soap to remove the oils from the fabric. The next three times I washed with about 1 tsp of detergent (to continue removing oils) and 1 tbsp oxyclean (to ensure the detergent was fully removed).  The last four washes I did with only water using the extra rinse feature to make sure all the soap and oxyclean was removed.  All washes were done with hot water and all dry cycled were done on hot so that the fabrics achieved maximum "quilting." 

(3) Cut all the fabrics to identically sized inserts. We drafted an ideal insert shape in AutoCAD (pattern shown below) and calculated the area for future absolute comparisons and testing but all fabrics for this test were cut using the same template so that we did not need to divide the results by area but rather could compare based on net absorption per insert layer. 

Transient
Transient

(4) Determine insert thickness. The purpose of this test was to determine the absorption PER INCH of THICKNESS of commonly used diaper insert fabrics.  All of the testing we were able to find online was based simply of the area of the insert, this meant that typically thicker fabrics did very well and thinner fabrics did poorly.  However, this ignores the fact that most inserts made with thinner material use more layers.  We wanted to correct for thickness so that we could answer questions such as  "What absorbs more? 4 layers of bamboo fleece or 2 layers of bamboo heavy fleece"

Measuring thickness of a compressible object like fabric is tricky because the thickness will vary based on how much pressure you place on the fabric.  We considered measuring the thickness in an uncompressed state but that wouldn't be practical since all inserts are typically under some pressure when stuffed in the pocket of a diaper.  We decided to measure all thickness with 15 lbs of pressure applied to the entire insert, this would approximate the pressure of the baby sitting on the inserts.  The applied pressure also gave us a more consistent distance that was easier to measure.

The set-up (shown below) is a two stiff base boards with several layers of inserts laid on top of them (however many I had on hand) then two stiff top boards and finally three 5lb weights applying a total of 15 lbs of pressure to the stacked inserts.  We then used a digital caliper, zero-ed to the width of just the boards, to measure the added thickness of the inserts in three places.  We recorded this measurement, divided by the total inserts measured, and calculated the average thickness of each insert layer.

The caliper zero-ed out to the thickness of the wood planks. 

The caliper zero-ed out to the thickness of the wood planks. 

The caliper measuring the thickness of the stacked layers of insert fabric, with 15 lbs of weight adding moderate compression. 

The caliper measuring the thickness of the stacked layers of insert fabric, with 15 lbs of weight adding moderate compression. 

(5) Determine the dry weight of the insert.  Next we weighed each insert, prior to testing, to get its dry weight.

Transient

(6) Determine the wet weight after 30 seconds submerged in water.  We submerged the dry insert in water for 30 seconds to determine the "rapid absorption" after 30 seconds, we lifted the insert and allowed it to drip for 30 seconds, then weighed it and recorded the weight. 

Insert layer soaking for 30 seconds.

Insert layer soaking for 30 seconds.

Allowing insert layer to drip for 30 seconds.

Allowing insert layer to drip for 30 seconds.

(7) Determine the wet weight after 3 minutes submerged in water.  Next we determined how much water the insert layer would absorb in "long term absorption" for this step.  Again we allowed the insert to drip for 30 seconds prior to weighing. 

(8) Determine the wet weight after 3 minutes in compression.  Finally we took the 3 minute soaked insert and sandwiched it between the same stiff boards used to determine thickness, applied the same 15 lbs of pressure for 3 minutes and weighed the insert to determine how much water it would  retain under the average compression of a baby butt. (images below show set-up)

The set-up for "compression testing."  Shown above is a cookie sheet, to catch the drips, then a layer of wood planks (spaced slightly apart to allow water to flow through) then a single soaked insert, next is another layer of wood planks and finally 15 lbs of weight adding the compression. 

The set-up for "compression testing."  Shown above is a cookie sheet, to catch the drips, then a layer of wood planks (spaced slightly apart to allow water to flow through) then a single soaked insert, next is another layer of wood planks and finally 15 lbs of weight adding the compression. 

(9) Repeat 3 times for each fabric type, record results, calculate conclusions.  We repeated the experiment 3 times for each type of fabric and calculated results based on the average of all three trials.  We recorded all the weights, then determined weight of the water absorbed by subtracting the dry weight from the wet weights.  Finally we divided the average weight of water absorbed by the average thickness of the insert to determine water absorbed per inch of fabric.  This final number is what we used for all of our comparisons.

Fabrics we tested

All pictures are taken AFTER the fabrics have been prepped (quilted).  You might notice pilling on the surface or curling at the edges, this will frequently occur on fabrics after they have been washed in hot water and dried on hot EIGHT TIMES! 

I did prep the un-faced Zorb fabric the same way I prepped all the other fabrics, this is AGAINST manufacturing recommendations because it is a non-woven fabric.  However, it seemed to work fine aside from some moderate piling.  I have no idea how this prepping affected absorption since I did not test an un-prepped sample of Zorb. 

Organic Hemp Fleece

Organic Hemp Fleece

Organic Hemp French Terry

Organic Hemp French Terry

Organic Bamboo/Hemp Blend Fleece 

Organic Bamboo/Hemp Blend Fleece 

Organic Bamboo Heavy Fleece

Organic Bamboo Heavy Fleece

Organic Bamboo Fleece

Organic Bamboo Fleece

Organic Bamboo Velour

Organic Bamboo Velour

Organic Bamboo Double Sided Terry

Organic Bamboo Double Sided Terry

Microfiber

Microfiber

Zorb

Zorb