Powder displacement

[kozybe]

Just wondering if anyone else has had this issue? I have brewed many batches from multiple different sources and with all of them my powder never melts to the ml it should. In other words, I always have to add more oil before filtering to make up for it so that I get my target volume at the end. Does this mean that the powder isn't as pure as I think?

 

[beedix]

Yes, purity can impact it. Plus the density numbers that are used for displacement are not always correct (often based on auto calculated numbers from chemspider).

You will also loose product in the filter which is not always a consistent amount. Syringe filters are usually less than filter top types just because the filter medium is larger.

 

[beedix]

Also watch out for adding oil to compensate as that can result in unintentional under dosing. Depending on your batch size it may or may not be insignificant.

 

[kozybe]

Thanks beedix. I use a 60 ml syringe and syringe filter to get the final product. So I draw up my solution in my 60 ml syringe before I put the filter on and for let's say a 50 ml batch I'll only have 43 ml or something. I'm pretty sure I'm not under dosing because I will always make sure that I have 3 ml less than the total to purge the filter with just oil at the end. I have even melted 10 grams of powder in a small beaker to see what it would melt to and it came up way short. That makes sense about chem spider, but my powder seems significantly off when it comes to displacement. Thanks for the input.

 

[beedix]

Yeah, with a 50ml batch, your loss will be insignificant. Sounds like its density variance as you suspect.

Another obvious potential source is from scale absolute accuracy.

 

[kozybe]

I suppose it might be the scale(just a cheap jewelry scale), but it's only a couple of months old and it's accurate to 0.01. I don't know? Now that I'm thinking about it... It is a little strange that all of my powder I've gotten has been over in weight though. Maybe I need to double check my scale?

 

[beedix]

Throw some check weights in similar quantity to the powder you use. Also "trickle" smaller check weights on a little at a time up to then desired amount and see how it responds. Even very good scales try to combat drift and can do so poorly and be much worse than absolute accuracy.

 

[kozybe]

Yeah good idea. I'll do that. I do know about the drift issue with scales. I have weighing boats so to be as accurate as I can I will weigh up the desired amount, then tare a new boat, and transfer the whole pile at once. It's usually pretty accurate, but when I weigh up my powder from a new order it's over by a lot. For example my last order was test e, test p, and tren ace. All were supposed to be 10 g but when I weighed them up it was 28 g each. I even emailed the source and he thought it sounded like a mistake because he said he always makes them a gram or so over, but not that much. I'm starting to think I need a new scale.

 

[kozybe]

Thanks again beedix. You sound like a pretty intelligent person. Appreciate your help.

 

[beedix]

No prob...hopefully it's the scale. That's a much easier problem then varying powder quality lol