The test process is clear and understandable, but what is the correct value after the test? That is, what are the absorption parameters that show whether the paper is normal and resistant to absorption or not? What amount of water absorbed is considered a normal value and what is not? Your help is very important.
Interesting Question. Unfortunately there is no straight answer to this. Every different application will need a specific type of paper with a specific COBB value (range). Eg. Blotting Paper has a very high COBB value (it can absorb the most). On the other hand Glassine Paper or Parchment Paper or Currency Note Paper have very low COBB value (it resists water absorption). So is low value correct or is high value correct ? Its application dependant. Corrugation Paper will have different values compared to the paper used to manufacture Paper Cores / Tubes. Paper that is to be printed needs a different COBB. Infact even the type of printing processes that will be used may need different COBB values. The buyer of paper needs to specify what he wants. And if he still faces issues in processing, then he needs to increase / decrease the COBB requirement accordingly. There is no "One Size Fits All" concept with COBB. Neither is "Higher The Better". Hope I was able to satisfy your query today.
We would also like to know about the function or purpose of COBB value in manufacturing a best carton from the same segment of papers... I.e. if the COBB is high then what would be the effect or if the COBB is low then what will happen to a same category Kraft-paper (100 gsm / 18 bf)
Sir,,, could you please suggest us that what should be a suitable COBB value for a 120 gsm, 18 bf kraft paper to perform it's best during monsoon climate & during dry weather and also tell us the suitable COBB value for 250 GSM, 28 bf papers.... I mean to say ,,, what should be our preferred COBB value for those above stated MATERIALS during the stated weather conditions to the paper mills (we are paper corrugated box manufacturer)
Sorry sir can i ask you about this video? what effect do the two papers have on this cobb test? I still don't understand it, i hope you see my comment. Thank you
Practical speaking you need blotting paper only on the wet side. But standard says sandwich the sample between 2 sheets. Maybe if the cobb value is very high the water will bleed from the dry side also and will be picked up by the second blotting paper. Doesn't hurt to use 2 sheets.
Hello Marcella. Moisture is the current moisture inside the paper/paper board. COBB is the "ability" to absorb "more" moisture. Hence they are very different.
@@marcella3928 Yes, to the best of my understanding, Ash Content will affect COBB values for sure. While I donot have data to support it, my judgement says higher ash content should lead to a higher COBB value.
If that's the case, that everyone has to specify his COBB range, what value does the test have? How can we verify the claims of a manufacturer who claims low absorbency against the standard if there are no absolute values that define as precisely as possible what the correct value is for the same type of paper/cardboard or at least in the same group of paper?
Yes, you have to know what value you want. Otherwise if the test says this is 30 COBB, how do you know if that is correct paper for your application ?. When you say "low" absorbency, it is very subjective. "Low" for you maybe "High" for me. or it could be "too low" for someone else. The way forward for you is : 1) Check what is the COBB value for your current supply. Now atleast you have a starting point. Let us say this value is X. 2) Then see if that paper is giving you any trouble. Analyse the problem being faced. If you think the paper should absorb less, then you can tell your vendor that you need a COBB value lower than X. Or you can try different papers and identify which paper (and its COBB value) is performing best for your application. 3) Make that value as YOUR OWN standard. I am sorry but the answer you seek from me is not available with anyone in the world. There can be no "Single Standard" or no agency (like ISO or ASTM or BIS etc) who can say that X COBB is correct and Y COBB is not correct. Because X may be right for some applications and Y may be right for some other applications.
That is because there is no such source of info. COBB is a value and whether the value is suitable to you depends highly on what you are using the Paper for ? Is it for Printing or Corrugation or forming Paper Cores, etc. Even if its printing, it depends on the type of ink or machine. Eg. Printing Currency Notes vs printing a magazine vs printing a news paper, all require different COBB values. And because of this virtually unlimited applications, there will be no one who can give you a definitive value for ALL applications. Something (COBB Value) that may work perfect for "You" may not work for someone else. You need to adopt a reverse engineering approach. Take the sample of paper which is known to "work" well. Test the COBB. Make it your benchmark. Hope I was helpful today.
@@Flat_Earth_Sophia Hello Addison, I am afraid there is non. Atleast to the best of knowledge and belief (and understanding on how we work on ASTM/TAPPI standard development committees :) )
Rather than saying we (At TAPPI / ASTM) dont want to establish standard values, I would say its a herculean task to do so. Next to impossible due to the sheer variety of papers / inks / machinery / applications.
Tissue paper has a very high absorptivity. This test is for printing paper or for paper used for corrugated boxes and paper cores. Not suitable test for tissue.
Sample being tested is 1/100th of a Sq.Mtr. Hence the gain in weight is to be multiplied by 100 to get the effective gain in weight if a 1 Sq.Mtr area was exposed to water. The theoretical units of COBB Test are also GSM (grams per sq. mtr), but in order not to confuse it with the Grammage GSM, it was decided to leave it as a unitless / index number. Hence we write the results as COBB = 80 or 80 COBB. Hope I was helpful. for any further assistance, you can write to us at info@packtest.com
@@donycandra3296 No Dony, The scientific terminology is that COBB is the amount of water absorbed by paper/paperboard when 1 square meter (1 Sq.Mtr) area of the paper comes in flooded contact with water such that the water forms a 1cm head over the surface. Now if we were to test a 1Sq.mtr area directly, the actual gain in weight would be the COBB value. However testing 1 Sq.Mtr area is not practically possible in a small lab. So the test area is reduced to 100 cm2 (which is 1/100th of a Sq.Mtr). So when you check the weight gain in this small area (100cm2), the gain is to by multiplied by 100 to get the effective water absorbed by 1 Sq.Mtr. To summarise. If I were to test 1 Sqmtr, then weight gain = COBB. if I test 1/100th Sq/Mtr (100cm2), then weight gain x 100 = COBB. Simple. Let me know if you need more explanation. I want to make sure you dont remain confused at all.
The test process is clear and understandable, but what is the correct value after the test?
That is, what are the absorption parameters that show whether the paper is normal and resistant to absorption or not? What amount of water absorbed is considered a normal value and what is not?
Your help is very important.
Interesting Question. Unfortunately there is no straight answer to this. Every different application will need a specific type of paper with a specific COBB value (range). Eg. Blotting Paper has a very high COBB value (it can absorb the most). On the other hand Glassine Paper or Parchment Paper or Currency Note Paper have very low COBB value (it resists water absorption). So is low value correct or is high value correct ? Its application dependant. Corrugation Paper will have different values compared to the paper used to manufacture Paper Cores / Tubes. Paper that is to be printed needs a different COBB. Infact even the type of printing processes that will be used may need different COBB values. The buyer of paper needs to specify what he wants. And if he still faces issues in processing, then he needs to increase / decrease the COBB requirement accordingly. There is no "One Size Fits All" concept with COBB. Neither is "Higher The Better". Hope I was able to satisfy your query today.
We would also like to know about the function or purpose of COBB value in manufacturing a best carton from the same segment of papers...
I.e. if the COBB is high then what would be the effect or if the COBB is low then what will happen to a same category Kraft-paper (100 gsm / 18 bf)
Sir,,, could you please suggest us that what should be a suitable COBB value for a 120 gsm, 18 bf kraft paper to perform it's best during monsoon climate & during dry weather and also tell us the suitable COBB value for 250 GSM, 28 bf papers....
I mean to say ,,, what should be our preferred COBB value for those above stated MATERIALS during the stated weather conditions to the paper mills (we are paper corrugated box manufacturer)
Sorry sir can i ask you about this video? what effect do the two papers have on this cobb test? I still don't understand it, i hope you see my comment. Thank you
Practical speaking you need blotting paper only on the wet side. But standard says sandwich the sample between 2 sheets. Maybe if the cobb value is very high the water will bleed from the dry side also and will be picked up by the second blotting paper. Doesn't hurt to use 2 sheets.
Excuse me, i wanna ask is a cobb value directly proportional to moisture or inversely proportional to moisture? Thank you.
And the ash content too, thank you.
Hello Marcella. Moisture is the current moisture inside the paper/paper board. COBB is the "ability" to absorb "more" moisture. Hence they are very different.
@@PackTest how bout the ash content value? If the ash content value is high then the cobb value will be high too? Or will be low? Thank you
@@marcella3928 Yes, to the best of my understanding, Ash Content will affect COBB values for sure. While I donot have data to support it, my judgement says higher ash content should lead to a higher COBB value.
Do you have ISO535 certificate for presented Tester?
ISO 535 is a Test method and not a certificate. Yes the COBB Test is as per ISO 535 as well as TAPPI T441
If that's the case, that everyone has to specify his COBB range, what value does the test have?
How can we verify the claims of a manufacturer who claims low absorbency against the standard if there are no absolute values that define as precisely as possible what the correct value is for the same type of paper/cardboard or at least in the same group of paper?
Yes, you have to know what value you want. Otherwise if the test says this is 30 COBB, how do you know if that is correct paper for your application ?. When you say "low" absorbency, it is very subjective. "Low" for you maybe "High" for me. or it could be "too low" for someone else.
The way forward for you is :
1) Check what is the COBB value for your current supply. Now atleast you have a starting point. Let us say this value is X.
2) Then see if that paper is giving you any trouble. Analyse the problem being faced. If you think the paper should absorb less, then you can tell your vendor that you need a COBB value lower than X. Or you can try different papers and identify which paper (and its COBB value) is performing best for your application.
3) Make that value as YOUR OWN standard.
I am sorry but the answer you seek from me is not available with anyone in the world.
There can be no "Single Standard" or no agency (like ISO or ASTM or BIS etc) who can say that X COBB is correct and Y COBB is not correct. Because X may be right for some applications and Y may be right for some other applications.
But why can I find nowhere online what exactly a good Cobb rating is?
That is because there is no such source of info. COBB is a value and whether the value is suitable to you depends highly on what you are using the Paper for ? Is it for Printing or Corrugation or forming Paper Cores, etc. Even if its printing, it depends on the type of ink or machine. Eg. Printing Currency Notes vs printing a magazine vs printing a news paper, all require different COBB values. And because of this virtually unlimited applications, there will be no one who can give you a definitive value for ALL applications.
Something (COBB Value) that may work perfect for "You" may not work for someone else. You need to adopt a reverse engineering approach. Take the sample of paper which is known to "work" well. Test the COBB. Make it your benchmark.
Hope I was helpful today.
@@PackTest Ah. What about for books? There must be a chart somewhere...
@@Flat_Earth_Sophia Hello Addison, I am afraid there is non. Atleast to the best of knowledge and belief (and understanding on how we work on ASTM/TAPPI standard development committees :) )
Rather than saying we (At TAPPI / ASTM) dont want to establish standard values, I would say its a herculean task to do so. Next to impossible due to the sheer variety of papers / inks / machinery / applications.
@@PackTestMachinesInc Then what is the point of the test, if the numbers mean nothing?
While we test our tissue paper then how much time do we need to keep on water
Tissue paper has a very high absorptivity. This test is for printing paper or for paper used for corrugated boxes and paper cores. Not suitable test for tissue.
Sorry sir please help me
To calculation (final wt - initian wt) x 100
please tell me where does the number 100 come from?
Sample being tested is 1/100th of a Sq.Mtr. Hence the gain in weight is to be multiplied by 100 to get the effective gain in weight if a 1 Sq.Mtr area was exposed to water. The theoretical units of COBB Test are also GSM (grams per sq. mtr), but in order not to confuse it with the Grammage GSM, it was decided to leave it as a unitless / index number. Hence we write the results as COBB = 80 or 80 COBB. Hope I was helpful. for any further assistance, you can write to us at info@packtest.com
So the number of 100 is the number of circumference of the circle?
Im so confused 😭😭😭
@@donycandra3296 No Dony, The scientific terminology is that COBB is the amount of water absorbed by paper/paperboard when 1 square meter (1 Sq.Mtr) area of the paper comes in flooded contact with water such that the water forms a 1cm head over the surface. Now if we were to test a 1Sq.mtr area directly, the actual gain in weight would be the COBB value. However testing 1 Sq.Mtr area is not practically possible in a small lab. So the test area is reduced to 100 cm2 (which is 1/100th of a Sq.Mtr). So when you check the weight gain in this small area (100cm2), the gain is to by multiplied by 100 to get the effective water absorbed by 1 Sq.Mtr.
To summarise.
If I were to test 1 Sqmtr, then weight gain = COBB.
if I test 1/100th Sq/Mtr (100cm2), then weight gain x 100 = COBB.
Simple.
Let me know if you need more explanation. I want to make sure you dont remain confused at all.
Thank you so much
Actually I want to know the size of paper while we cut it
Thank you sir❤
Thank you sir plasse help me
Yes Sure. You can email us on info@packtest.com or call me on 9824069001. If you are outside india dial +919824069001
VALUE
Pls send an email to us at info@packtest.com
Can you help me sir.?
In give me link mead in paber
And thanks for you
I am sorry I did not understand. What do you need ?