Boiling and Filtration - Kshara Preparation 3/5

By Dr Ankita

Classical information

After the ashes of the plant have been collected, they are soaked in water, mixed well, filtered and later boiled. The table below summarises what has been collected from various texts that mention kśār preparation.

						Filtration
Sr.No	Text name	Time to soak	Ash: Water ratio	Filtration number	Filtration cloth fold	Filtrate nature
1.	Sushruta Samhita	-	1:6	21	1	red in colour, sharp & gluey
2.	Rasataringini	3 hours	1:4	1	3	clear
3.	Ayurveda  Prakash	Overnight	1:4	1	1	-
4.	Rasahridayatantra	Overnight	1:8	1	1	-
5.	Ayurveda Sarasanghraha	3 days	1:8	7	4	clear
6.	Ashtang Sangraha	-	1:4:4 Ash:water:gomutra	1	1	Filter till liquid is clear
7.	Bhaishajya Ratnavali	-	1:4/1:6	1	1
8.	Sharangdhar Samhita	Overnight	1:4	1	1	Clear

After the filtration is done, the collected clear liquid is now called as Pāniya Kśār which is meant for internal consumption and later this liquid is subjected to boiling to transform it into Mrudu, Madhyama and Tīkśna kśār, each with increasing potency than the previous one and now this kśār is called as the Pratisārniya Kśār which is meant for external application. 

			Boiling methods
#	Text	Boiling	Vessel for boiling
1	Sushruta Samhita	heating is done again, and the strained mixture, i.e., white Kshara, is collected.	Iron vessel
2	Rasataringini	heat on low flame till kshar is formed	Iron vessel
3	Ayurveda Prakash	heat continue up till dryn Kshara is formed	Earthen pot
4	Rasahridayatantra	heat the collected liquid.The mixture then becomes thick; dry it in sunlight till pure white color Kshara which is granular in texture is obtained	Iron vessel
5	Ayurveda Sarasanghraha	The liquid is heated till it becomes thick and is dried in a broad vessel	Earthen pot or steel vessel
6	Ashtang Sangraha	Boil till kshar is formed	Iron vessel
7	Bhaishajya Ratnavali	Heat till kshar is formed	Iron vessel
8	Sharangdhar Samhita	Heat on mild fire till kshar is formed.	Earthen pot

What we did and observed

It was difficult to find detailed information on the method of filtration and boiling that is being used by the industries for kśār preparation. In our set up, we added 6 parts of water to 1 part of ash. After thorough mixing, this liquid was strained through a thin cotton cloth. Filtration was performed 21 times. Each time, the cloth was folded 8 times and the filtrate allowed to pass. The cloth was rinsed between successive filtrations.  An electron microscopic examination of the cloth filter used for water filtration made of an old saree which had undergone multiple launderings demonstrated an effective pore size of 20 micrometers when folded four to eight times. When the cotton cloth is washed multiple times, its threads become soft and loose, decreasing the pore size. This explains the need for fold filtration and the specific use of cotton cloth for the process during the ancient times. The kśārōdak contains carbonates of sodium, potassium, calcium and magnesium. Boiling causes the carbonates to be released as carbon dioxide thereby concentrating the potassium, calcium, sodium and magnesium in it which contribute to the kśāratva of the kśār.

Gaps Identified

• Although the literature talks about the use of cotton cloth for filtration, its dimensions in terms of its size and the pore size have not been mentioned.We also don’t find any references which state whether each time the kśār was being prepared, if the same old cotton cloth was taken or a fresh one was used instead. 

• There is no consensus for how long we should soak the ashes as well as the source and type of water one must use for soaking.

• The exact time required for boiling is not mentioned clearly in the classical texts. The lack of these output parameters means that we cannot assess if filtration and boiling is done properly for good quality of kśār. 

• Some texts mention the use of gomutra along with water for soaking. It can be because it contains elements like potassium, calcium, magnesium, sodium with potassium being in the highest concentration. It is unclear how many practitioners or industry deploy this addition. 

  
  

Proposed ways to address gaps

• We have to clearly state the source and the nature of water that has to be used for soaking. Weight/ volume or volume/volume measurements have to be clarified. 

• For filtration, it would be helpful to know filtration medium material, particle size of the filtrate and the pore size of the filtration material. The quality of the filtrate can be standardised by knowing it’s pH, OD (via spectrophotometer), colour, clarity and density. 

• Similar information for the matter after boiling would be useful.