How to remove dried old mortar off used brick?

How to remove dried old mortar off used brick?

Assuming that gently chipping it off is taking too long...you might try a solution of 20 percent hydrochloric acid (wear gloves, and eye protection) soaking the bricks in the acid solution should loosten the mortar enough to make it easily come off. remember
if you are diluting the acid ALWAYS pour the acid into the WATER NEVER the WATER into the ACID! Another way, if you have one available is to use a Needle Scaler
this is either electric, or more commonly Air powered and has numerous 'needles'
(actually they are more like the size of uncooked spaghetti, and they vibrate and impact the mortar and remove it.

Assuming that gently chipping it off is taking too long...you might try a solution of 20 percent hydrochloric acid (wear gloves, and eye protection) soaking the bricks in the acid solution should loosten the mortar enough to make it easily come off. remember
if you are diluting the acid ALWAYS pour the acid into the WATER NEVER the WATER into the ACID! Another way, if you have one available is to use a Needle Scaler
this is either electric, or more commonly Air powered and has numerous 'needles'
(actually they are more like the size of uncooked spaghetti, and they vibrate and impact the mortar and remove it.