How to accurately weigh powders using a milligram scale?

[GuatamatheStoic1]

I have a lot of trouble weighing powders with my milligram scale, it tends to jump around by 50 or so milligrams at random. It wasn't a super cheap $2 scale, but it's also not exactly a laboratory-grade analytic scale. In addition, I tend to lose a fair bit of powder when weighing it out, e.g. transferring it between containers. Is there a good technique I can use to avoid these errors? Or should I just get a better scale?

 

[Pickledlemons]

I found my milligram scale to be rather inaccurate too.. It didn't seem to register anything under 7mg which was a problem because I was trying to weight 1mg of alprazolam powder. What do you need it for? If its for a drug to be taken orally you can weight a larger amount, mix with water and dose by ml.

 

[Tubbs]

Yeah the only way you're gonna get close is with a lab grade scale man... alot of the ones you can buy have a pretty high margin of error.

 

[MrRoot]

Most of the mg scales aren't accurate with the smallest weights and I have noticed that they work more accurate if there is more weight.

One way to make them more accurate is to use something as a extra weight and so you can put for example few coins or a lighter on a scale and then press the tare button and weight what you are weighing.

Still doesn't work with few mgs and it is better to weigh more and then use volumetric dosing by weighing for example 25mgs and then dissolving that powder to 25ml of liquid (water or PG for example depending on the solubility and use) and then you have 1mg/1ml solution. Then you just dose 1ml for 1mg needed.

 

[GaryGlisten]

I use a Gemimi type scale which cost about ?14. on ebay. I have found the best way is to weigh half a gel cap and then add the substance to the gel cap using a 10mg scoop, then subtract the weight of the half a gel cap. It helps to keep removing the cap from the scale and put it back again so you get a general idea of the weight, otherwise the scales can get stuck, especially at very low weights. I know it's not a perfect solution but you just have to trust your judgement and take your time over it.

 

[simco]

Without spending a lot of money, it will be very hard to get a scale that can weigh out very small quantities (say, <10mg or so) accurately. You might try adding a bit of weight to the scale when you measure, and then simply subtract the additional weight.

That said, if you're not splurging on a lab-grade scale, I recommend looking at scales intended for weighing gunpowder for home bullet making. I've had very good luck with bullet-making scales...they're not too expensive and I've found them to be quite accurate.

 

[Chris42393]

I bought this Digital MG scale off of amazon and it has been perfectly accurate.

https://www.amazon.com/gp/product/B071WTJNYG/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

and i bought a calibration weight set to make sure it was accurate too.

https://www.amazon.com/gp/product/B003STEJAC/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1

Have had no problems with it and it has been reliable. I am posting the websites for HARM REDUCTION. Not trying to sell anything.

Both about $30 total. If you need to weigh accurately, it would be a good investment.

 

[Tranced]

Milligram scales are not accurate, even the ones I bought for ?150 weren't very good. There is a trick to them though, and it pretty much comes with knowing them. When I put the weighing pan on mine I know that it will register at 2013mg. If I add 20mg of powder to that then it should read 2033 milligram - I have to repeatedly take the weighing pan off and turn the scales back on (be sure to let them warm up) - to get it right. I trebble check+ everything I do, and sometimes the scales just don't want to play at all. If its jumping by 50mg then your scale is probably broken and/or you're moving around too heavily/breathing on the scale etc.

Tips:

- leave your scales on for 30~ seconds before using.
- reweigh
- recallibrate
- carefully clean powder off the plateau
- weigh on top of something heavy i.e a weighing pan. The closer your scales are to half their capacity is their most accurate
- don't move around/breathe on them
- etc

To prevent powder loss, just simply scrape it into a gel cap.

 

[MDPV_Psychosis]

Milligram scales are not accurate, even the ones I bought for ?150 weren't very good. There is a trick to them though, and it pretty much comes with knowing them. When I put the weighing pan on mine I know that it will register at 2013mg. If I add 20mg of powder to that then it should read 2033 milligram - I have to repeatedly take the weighing pan off and turn the scales back on (be sure to let them warm up) - to get it right. I trebble check+ everything I do, and sometimes the scales just don't want to play at all. If its jumping by 50mg then your scale is probably broken and/or you're moving around too heavily/breathing on the scale etc.

Tips:

- leave your scales on for 30~ seconds before using.
- reweigh
- recallibrate
- carefully clean powder off the plateau
- weigh on top of something heavy i.e a weighing pan. The closer your scales are to half their capacity is their most accurate
- don't move around/breathe on them
- etc

To prevent powder loss, just simply scrape it into a gel cap.

I agree with with this and some other stuff that people have said so far. I wanted to add one more tip/method I've discovered:

You don't want to add small amounts of powder to the pan while it's already on the scale. For some reason, these scales don't register small changes very well.

Weigh your empty clean pan numerous times after a proper calibration and make sure you know exactly how much it weighs. It's better to weigh the stuff on the pan and then subtract the weight of the pan. Taring the scale to 0 with the pan on doesn't seem to be so accurate... These scales seem to work better in their mid-range like Tranced said.

For example:

1) Make sure scale is on a level stable surface and make sure there is no breeze. Allow scale to adjust to room temperature if it was stored somewhere hotter/colder.
2) Turn on scale, let it warm up a bit and then recalibrate.
3) weigh pan and make sure it weighs what you expect it to
4) take pan off scale. Dump powder on pan.
5) place pan back on scale and note new weight. Take pan off scale. Subtract known weight of pan from the weight you just measured.
6) if it weighs too much then take away some. If it weighs too little then add some.
7) place pan back on scale and reweigh.
8 ) go back to #6 if the weight still isn't correct.