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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Help need with Math equation for moisture content
#26740862 - 06/12/20 11:24 PM (3 years, 7 months ago) |
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I’m attempting to dial in my spawns moisture as again have had a bad bout with bacteria, so I understand I can calculate the moisture in grain by mass wet-mass dry/mass dry but I can’t figure out how to get to the water that would be need to be added to achieve the desired wet weight and moisture content. I’m shooting for 6qt spawn bags so 2688g wet spawn at moisture content of 47% the beginning moisture content in the grain is 10% if someone could explain how to come to the water that needs to be added and dry material that would be great
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solipschism
Prodigal Son

Registered: 05/22/20
Posts: 26
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26740887 - 06/13/20 12:03 AM (3 years, 7 months ago) |
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Given grain mass m_g and water mass m_w:
m_g + m_w = 2688 (the total mass of the components is equal to 2688g)
and
0.1*m_g + m_w = 0.47*2688 (the mass of water in the components is equal to 47% of 2688g)
yields
m_g = 1583g, m_w = 1105g
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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Re: Help need with Math equation for moisture content [Re: solipschism]
#26741179 - 06/13/20 07:00 AM (3 years, 7 months ago) |
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Thank you. I tried it by just equating it into 100 parts such as at 10% content I need to add 37g bring me to 137 than divided 2668 by 137 to get 19.***** so took 37*19 and 19*100 giving m_g=1950 m_w=725, seems you got math knowledge I’m sure this is incorrect but can you explain why I can’t do it this way? Thank you.
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bodhisatta 
Smurf real estate agent


Registered: 04/30/13
Posts: 61,889
Loc: Milky way
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26741219 - 06/13/20 07:25 AM (3 years, 7 months ago) |
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Beginning MC is 10% So if you have 1000 grams of grain its really 100 grams water and 900 grams dry grain.
Water / water+grain = 10% 100 / 100+900 = .10
Water / water+grain = 47% X / X+900 = 0.47 X = ~ 800
800-100=700 grams of water to add
So now you have 1000 grams of grain 100 was water 900 was dry grain You add 700 grams of water You have 1700 grams of grain 900 is dry grain 800 is water 800 water / 1700 new total weight = ~ 47%
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solipschism
Prodigal Son

Registered: 05/22/20
Posts: 26
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26741528 - 06/13/20 10:11 AM (3 years, 7 months ago) |
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Quote:
PiptheGreAtest said: Thank you. I tried it by just equating it into 100 parts such as at 10% content I need to add 37g bring me to 137 than divided 2668 by 137 to get 19.***** so took 37*19 and 19*100 giving m_g=1950 m_w=725, seems you got math knowledge I’m sure this is incorrect but can you explain why I can’t do it this way? Thank you. 
Bod covered it, but in case this is easier to parse:
The way you're trying to figure it out assumes that you're replacing dry mass with water mass, rather than adding water, so it doesn't work.
If you have 100g grain comprised of 10% water, you have 90g of dry mass and 10g of water.
Adding 37g of water, you end up with 137g total, comprised of 90g dry mass and 47g water.
The new moisture content is 47/137=0.34, so adding 37g of water only brings you to 34% moisture content. To find the amount of water you'd need to add to get to 47%, you need to find m_w such that
(0.1*m_g + m_w) / (m_g + m_w) = 0.47
If the initial moisture content is c_i and the desired moisture content is c_f, then the general formula is going to be
m_w = ((c_f - c_i)*m_g) / (1 - c_f)
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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Re: Help need with Math equation for moisture content [Re: solipschism]
#26742336 - 06/13/20 05:55 PM (3 years, 7 months ago) |
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Quote:
solipschism said:
Quote:
PiptheGreAtest said: Thank you. I tried it by just equating it into 100 parts such as at 10% content I need to add 37g bring me to 137 than divided 2668 by 137 to get 19.***** so took 37*19 and 19*100 giving m_g=1950 m_w=725, seems you got math knowledge I’m sure this is incorrect but can you explain why I can’t do it this way? Thank you. 
Bod covered it, but in case this is easier to parse:
The way you're trying to figure it out assumes that you're replacing dry mass with water mass, rather than adding water, so it doesn't work.
If you have 100g grain comprised of 10% water, you have 90g of dry mass and 10g of water.
Adding 37g of water, you end up with 137g total, comprised of 90g dry mass and 47g water.
The new moisture content is 47/137=0.34, so adding 37g of water only brings you to 34% moisture content. To find the amount of water you'd need to add to get to 47%, you need to find m_w such that
(0.1*m_g + m_w) / (m_g + m_w) = 0.47
If the initial moisture content is c_i and the desired moisture content is c_f, then the general formula is going to be
m_w = ((c_f - c_i)*m_g) / (1 - c_f)
Ok so I see how Bod came to the 700 but I have 2 unknown variable(m_w&m_g) so I have my grains final desire weight six quarts or 2688g do I need to just troubleshoot equation until I reach my desired final weight?
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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26742342 - 06/13/20 05:57 PM (3 years, 7 months ago) |
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Also I’m looking into sourcing large quantity of coir, I was hoping to get the moisture content down also in the substrate. What ratio should I run to a 6 quart bag in a patsytub? Desire substrate moisture content in percentages? I can oven test that also right if I continually run the same coir blocks right?
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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Re: Help need with Math equation for moisture content [Re: solipschism]
#26742530 - 06/13/20 07:24 PM (3 years, 7 months ago) |
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Quote:
solipschism said: Given grain mass m_g and water mass m_w:
m_g + m_w = 2688 (the total mass of the components is equal to 2688g)
and
0.1*m_g + m_w = 0.47*2688 (the mass of water in the components is equal to 47% of 2688g)
yields
m_g = 1583g, m_w = 1105g
Is this correct or do these equation that were posted later sorry like 3 ways of doing it!
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PiptheGreAtest
Aspiring Heavyweight


Registered: 07/18/16
Posts: 464
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26742578 - 06/13/20 07:47 PM (3 years, 7 months ago) |
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Quote:
solipschism said: Given grain mass m_g and water mass m_w:
m_g m_w = 2688 (the total mass of the components is equal to 2688g)
and
0.1*m_g m_w = 0.47*2688 (the mass of water in the components is equal to 47% of 2688g)
yields
m_g = 1583g, m_w = 1105g
Doing these equations is having me add more water than beforehand and I was have a horrible issue with bacteria. I’m attempting to create 6lb spawn bags before I was creating 4lb with 1125 grain to 525 water and it was horribly wet what’s wrong with this picture?
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solipschism
Prodigal Son

Registered: 05/22/20
Posts: 26
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Re: Help need with Math equation for moisture content [Re: PiptheGreAtest]
#26742616 - 06/13/20 08:12 PM (3 years, 7 months ago) |
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Quote:
PiptheGreAtest said:
Quote:
solipschism said: m_w = ((c_f - c_i)*m_g) / (1 - c_f)
Ok so I see how Bod came to the 700 but I have 2 unknown variable(m_w&m_g) so I have my grains final desire weight six quarts or 2688g do I need to just troubleshoot equation until I reach my desired final weight?
For this, if you plug in your known values of c_f, c_i and m_g (all of which you should know at the outset), this tells you how much water must be added - there is only one variable remaining.
Quote:
PiptheGreAtest said: Also I’m looking into sourcing large quantity of coir, I was hoping to get the moisture content down also in the substrate. What ratio should I run to a 6 quart bag in a patsytub? Desire substrate moisture content in percentages? I can oven test that also right if I continually run the same coir blocks right?
If you can work out your initial moisture content with an oven test, the above formula will work for getting it to a desired moisture content, too. Coir doesn't seem to hard to hydrate properly by eye/feel, though.
Quote:
PiptheGreAtest said: Doing these equations is having me add more water than beforehand and I was have a horrible issue with bacteria. I’m attempting to create 6lb spawn bags before I was creating 4lb with 1125 grain to 525 water and it was horribly wet what’s wrong with this picture?
Possibilities I can think of:
- Uneven moisture distribution, either from one grain to another or within each grain.
- The reason the bacteria took hold is something other than the moisture content of your grains.
- When you're saying "47% moisture content" you're intending to mean "47g of water for every 100g of dry mass" rather than "47% of the total mass is water", which are very different things. Everything I've said so far has assumed the latter.
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