How to weigh very small amounts

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JillGat

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I have a KD7000 Scale, which should measure down to 1g. When I am adding liquid very quickly, it will read as each gram is added. But if I have to measure out 1 gram only in a new container, I start with an eyedropper, but it does not register the first few grams. So I don't get a reading at all when I start slowly. Then all of a sudden it reads 5g. My earlier scale did this, too, so I bought this new one and I have the same problem.

Any advice welcome!
 

toxikon

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A scale like this would be handy to add to the arsenal: http://a.co/4VRzDiW

It measures down to .01g so it would be great for small amounts. I've thought about grabbing one myself, for when I just want to make one lotion bar or whatever.
 

Saranac

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Sometimes it's easier to measure from the container while it's on the scale.

I would put the entire container of the ingredient on the scale (take note of the original weight) and zero it out.

Then, using your pipette, remove the ingredient from the container. As you remove some of the contents, the scale will show a negative weight--just ignore the negative sign.

If in doubt of the accuracy, you can reweigh the container and subtract the new weight from the starting weight--the difference is how much you removed.

Hope that makes sense!
 

shunt2011

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I use a jewelers scale for small measure. You can get them for 10.00 or so on Amazon. I use mine for lip balms.
 

beardguy

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I have a similar scale to yours and I have the same issue. I use the lightest and smallest container, zero it, and I remove it after adding each bit of the material I want to weigh (FO, EO, additives). I don't know why, but it seems to register better that way and avoid having a 2-5g jump at one time.

I have also found that going by volume and then using the scale to verify works better than using a pipette and going slowly. I rough it out and then make sure with the scale. I would not recommend do it that with lye though.
 

makemineirish

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JillGat

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A scale like this would be handy to add to the arsenal: http://a.co/4VRzDiW

It measures down to .01g so it would be great for small amounts. I've thought about grabbing one myself, for when I just want to make one lotion bar or whatever.
You guys are the Bomb! I've complained to Brambleberry, to other soapers, etc. and never found anyone who could answer this question. I see now that scales are geared towards higher weights or lower weights and work best within those ranges. Makes total sense. I just need to get a cheap jewelers' scale like this one above.

You can stop reading now if you aren't interested in science nerdery.

As an epidemiologist and clinical researcher, I know that some medical lab tests are weighted toward being sensitive or specific. There is no one value for positive or negative, so you need to do two tests to get an accurate result.

As an analogy, a sensitive test would be like shooting a sparrow with a shotgun. You would likely hit the bird, but you'd hit a lot of other stuff, too. A specific test is like shooting a sparrow with a 22 rifle. You wouldn't hit a lot of stuff you didn't want to shoot, but you might not hit the sparrow, either. (Sorry for the killing analogy.)

An HIV test, for example, is a sensitive test. It will find all the positives, but it may find some false positives, too. So if your test is negative, it's pretty conclusive that you don't have it. If you test positive, we don't know if it's a true positive or a false positive, so we do a second, specific test. The specific test weeds out the false positives and gives us the true positives. So if you test positive on this second test, it means you have it.

Sorry, but I'm retired and I don't get to talk like this as much anymore! Thanks for the opportunity. :wink:
 

DeeAnna

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Actually, it's not really about the max capacity of the scale and more about its precision. I have an elderly digital lab scale that can weigh to 0.01 gram up to 2.2 kilograms. I love it because I can use this one scale for pretty much anything I do for soaping and lotion making. Much more convenient.

But the cost is fairly high to buy a higher precision scale with a large capacity. I couldn't afford my scale I have if I had to buy the modern-day brand-new equivalent. I am suspicious of the extra cheap jeweler's scales -- to some extent you get what you pay for. But if you're careful with them and check their accuracy from time to time, they'll be okay.

If you want to weigh to a precision of + or - 1 gram, you can't use a scale that reads to a minimum of 1 gram. You have to use a scale with a display that reads to 0.1 gram or better.

If you weigh by subtraction as Saranac explained, it's important to first tare the total weight of the container AND the pipette (or whatever utensil you're using to remove the material from the container.)

Put the container of oil (for example) on the scale, put the pipette in the container, and tare the scale. Then remove some oil from the container with the pipette, empty the pipette, and put the used pipette back into the container. Record that weight - that is the accurate weight of the oil that was transferred.

If you set the pipette to the side and only weigh the container without the pipette, you are not accounting for the amount of residue that remains in the pipette. That residue will vary as you use the pipette. That is not a big deal if you're weighing out 500 grams of lard for soap, but it is a big deal when weighing out tiny amounts of ingredients, such as EOs or preservatives or whatever.

Sometimes it's easier to measure from the container while it's on the scale.

I would put the entire container of the ingredient on the scale (take note of the original weight) and zero it out.

Then, using your pipette, remove the ingredient from the container. As you remove some of the contents, the scale will show a negative weight--just ignore the negative sign.

If in doubt of the accuracy, you can reweigh the container and subtract the new weight from the starting weight--the difference is how much you removed.

Hope that makes sense!
 

Saranac

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DeeAnna said:
If you weigh by subtraction as Saranac explained, it's important to first tare the total weight of the container AND the pipette. . . .)
Thank you for that!

DeeAnna said:
I am suspicious of the extra cheap jeweler's scales -- to some extent you get what you pay for.
Yep. I own one and I hate it. It constantly drifts weights so I have to keep track of the weight of the empty container. Once I've weighed out my ingredient, I have to unload the scale, shut it off, turn it back on, reweigh the container, and subtract the container weight. It's a pain, but I only use it for small test batches of lotion and such.
 
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