How accurate must the measuring be?

[daisy8]

Does everyone have a scale that allows measuring to be in part ounces or part grams. (I use grams). When one puts a recipe thru soapcalc, the measurement for water and NaOH almost always has a decimal side to it e.g. 67.086 grm for lye. I am sure ounces would work the same way.

Is it vital to keep all the measurements throughout the recipe absolutely spot-on? I can't see how anyone can because there is always a residue to oils or lye water when the oils and lye are mixed or when oil has to be poured from one container to another.

Is the norm, just to keep everything as accurate as possible?

Thanks.

 

[lsg]

For lye I always round down, for instance if the recipe calls for 67.086 grams of lye I would round it down to 67 grams. If the recipe called for 67.91, I would probably use 67.9 grams of lye.

 

[theath2010]

I use ounces and always round to the second decimal place when using my scale.

 

[Sapwn]

They don't seem to worry about accuracy ...


[ame]http://www.youtube.com/watch?v=0CLhaJjSZK0[/ame]

 

[Moody Glenn]

For lye I always round down, for instance if the recipe calls for 67.086 grams of lye I would round it down to 67 grams. If the recipe called for 67.91, I would probably use 67.9 grams of lye.

I do the same except, for simplicity, I would go farther and go to the nearest whole number. Like lsg's example I would go to either 67 for 67.086 and 68 for 67.9 (even if was 67.50). I would add a tiny bit extra of an oil to compensate. When dealing with gram weight a fraction of a gram is really not that much. When dealing with ounces then you will really need to be more accurate. If your scale can measure in grams I would suggest you use this instead of ounces.

 

[dagmar88]

They don't seem to worry about accuracy ...

So?




I weight everything under 3 kg with a scale with a 0.1 gram accuracy.
Very small quantities, like FO's and colorants, with a measuring spoon that goes down to 0.01.

 

[nebetmiw]

One reason I bought SoapMaker 3 was because soapcal was not accurate enough for my scale. With SM3 I am able to adjust the scale so the amounts work better. It has made a differance for me as my scale did not do decimals but fractions. I have since bought a new scale which works even better and have seen a improvment in my soap.

 

[daisy8]

My scale is good except that it doesn't weigh part grams. I looked around for one, but our local shopping centre didn't have though they are to be found online for quite a high price. Will definitely look around for a graded spoon though, I didn't know they existed.

Soapmaker3 sounds like a very good programme.

 

[dagmar88]

They're cheap too :smile:

http://www.ebay.com/bhp/digital-spoon-scale

 

[JennH]

When I use soapcalc I first create my recipe using percentages. Once I have one I like, I switch over to grams and round up or down to get rid of the decimals. Then I calculate again.

I still have to round up water and down lye since they still will have a decimal, but at least the oils are really straightforward for me.

 

[100%Natural]

It is not necessary to be spot on, but you still have to be careful. My rule of thumb is that I round down to nearest gram for the lye, down to the nearest ounce for water (this one isn't overly crucial) and up to the nearest ounce for oils.

Up with oils, down with lye!

 

[judymoody]

I do the same except, for simplicity, I would go farther and go to the nearest whole number. Like lsg's example I would go to either 67 for 67.086 and 68 for 67.9 (even if was 67.50). I would add a tiny bit extra of an oil to compensate. When dealing with gram weight a fraction of a gram is really not that much. When dealing with ounces then you will really need to be more accurate. If your scale can measure in grams I would suggest you use this instead of ounces.

+1. I like how you think, Moody Glen!

 

[Skatergirl46]

A gram is a small unit of measurement and you can get pretty accurate just rounding up for oils and down for lye (what I do). The fudge factor when rounding grams is very small. An ounce is 28.3 grams, a significantly larger unit of measurement. I would recommend using grams as well.

 

[Dr.J]

When you consider the variation in reported sodium saponification values for oils (and the variation is no doubt real across different sources, seasons, etc.), you find that a little rounding on weight measurements is not very significant.

For instance, I just did a google search for "saponification value of coconut oil", and the very first two hits gave 0.1911 and 0.181, a difference of over 5%!

As most have indicated, rounding up oils and down lye is the "safer" approach.

 

[DeeAnna]

And also recognize that the typical NaOH we use is not 100% pure. The usual analysis is 95% to 97% minimum purity with the balance being salt (NaCl), carbonates, and a tiny fraction of 1% of metallic impurities, mostly iron. These impurities also add a safety factor -- an additional hidden "superfat", so to speak, of up to 5%.

 

[daisy8]

The lye (NaOH) is bought from a chemist - it's 98% pure. It's as well priced as the lye which can be bought in the supermarkets here (UK). Thanks Dagmar88 for the link, I saw them and they are better than the ones which can be bought here.

Up oils and down lye is a good way to remember what to do! - Thanks