Below is a Gursikh's experience with Sarbloh
Sarabloh and VibrationMy initial angle would be to suggest that as a vegetarian, iron is usually a problem. I know in my family my parents both take iron pills and I too used to be low on iron. That gets solved. Compared to other common cooking materials like aluminum (which is in fact negative on the health) and stainless steel (no real effect), sarbloh is the best. Doesn't take all that much effort to use.
Secondly are the spiritual benefits. Now of course sarbloh must be a special thing because Guru Sahib chose it for amrit when he could have used gold or anything else. Clearly amrit being the most valuable physical thing in the world would deserve the most precious and suitable material to prepare and hold it. Guru Sahib specifically picked sarbloh. Even when referring to Vahiguru, Guru Sahib calls him sarbloh. Amrit can ONLY be prepared in this material and even in all amrit sinchaars by any jathebandi, the degh at amrit sinchaars is also given out in sarbloh batas because that's been a tradition since the start. Sarbloh is clearly important and special.
How so? A good example someone gave me was this: if someone asks a homeopathic doctor how his medicine works, he'll say it's the vibration. They take something and dillute it until it's physically not even noticeable anymore and then that is what they use for the medicine. What's left of the original? Just the vibration. Water conducts vibration and leaves a vibration. I think that's partly why we accept dry rations and things like oil but water based things are not used (my own understanding and not really relevant to her I guess).
Amrit was prepared in sarbloh by amritdhari gursikhs reciting bani and it leaves a vibration of naam on the person. That vibration becomes stronger or weaker depending on how much naam/bani they do and if they preserve that vibration by keeping Guru Sahib's rehit which is designed to keep that vibration.
The words we say, our emotions and thoughts all influence the food we prepare. There was a study by a Japanese scientist (I can find teh link if required) that showed words and the emotion behind them directly influence water particles in a very visible way. So if amrit is prepared by bani and sarbloh, the same way spiritual poison can be prepared by a manmukh with bad thoughts and using an inferior vessel.
When we eat sarbloh bibeki food, it's food cooked with naam/bani by an amritdhari and that food is designed specifically to increase the naam vibration. If someone has a lot of naam kamaiee then that is also felt in teh food. Examples are of Baba Ram Singh in Ranglay Sajjan when he used to make the daal with his singhnee, naam would start to go automatically in the eater. Or the example of Dr. Surinder Singh and the milk he gave to the rickshaw puller which gave him an amazing spiritual experience
So sarbloh bibeki food is an important tool Gursikhs use to propel their naam kamaiee.
Another point on sarbloh is that it's a natural conductor. Vibrations of a non-spiritual kind or heat are all very easily passed through iron. The same way, naam/bani vibrations, I suspect, are most effectively passed into the food when in sarbloh.
Even non spiritual people upon touching sarbloh feel a very strong sensation from it. The example of that witch that came to Weston (Historian) once comes to mind.
In a general sense though, Sarbloh is Guru Sahib's rehit. If we keep any of Guru Sahib's rehits then that by itself is something that earns Guru Sahib's blessings and kirpa. If it makes Guru Sahib happy, then what more do we want even if we ignore all the practical benefits?
One thing that people ask is what if there is someone who has best intentions for you and is good but not amritdhari. My answer to this is that such a person may not make 'bad' food with negative vibrations, but because they have not been given amrit and that naam vibration has not been given to them, they cannot pass that essential naam vibration on through the food. This vibration is an actual thing that can be felt by some Gursikhs like Baoo Mul Singh jee could tell if someone was amritdhari just by touching their head or their body. So even if they have great intentions and even love for you, they can't give that spiritually uplifting and necessary vibration we're looking for in our food.
Just like naam vibration was initially given by ingestion, I suspect that the most effective physical method of passing that vibration on is through food. Of course the most effective way at increasing the vibration is doing our own naam vibration through abhyaas at amrit vela (and notice that on a good amrit vela day naam goes by itself) It can get stronger or weaker by the food we eat.