Scroll of cleansing

The scroll of cleansing is a members only Dungeoneering reward, and can be purchased for 20,000 Dungeoneering reward tokens. It requires a Herblore level of 49 and a Dungeoneering level of 49, although it requires at least level 56 Dungeoneering to earn enough tokens to buy it. Once used, the scroll will disappear, giving the player the following permanent effects:


 * A 1 in 8 (12.5%) chance that the player will make a potion twice as fast as usual.
 * A 1 in 10 (10%) chance that when adding an ingredient to a vial of water, coconut milk, or unfinished potion, it will not be used up, leaving the player with an extra ingredient. This effect includes juju potions and extreme potions and can potentially save both the herbs and secondaries while making juju potions. This can be extremely advantageous considering Juju herbs must be grown by the player at a limited rate.

When using large numbers of ingredients, the scroll's saving ability can appear to have a higher chance than 10% (1/9). This is because each saved ingredient also has a 10% chance of being saved again. For example, if 1,000 ingredients are used, 100 should be saved because of the scroll. However, the 100 saved ingredients also have a 10% chance of being saved, so after using them there would be 10 more. Likewise, on average 1 of the 10 ingredients saved from the 100 would be saved. This adds up to an expected 11 $1/9$ % rate of herb saving when the savings are compounded, which means only 90% of the ingredients would be needed with the scroll. For example, if you had 1000 vials of water, 1000 herbs and 1000 secondary ingredients, the normal result would be 1000 potions. With the scroll of cleansing, you would only need 90% of the herbs and secondary ingredients, so you would only need 900 herbs and 900 secondary ingredients to yield 1000 potions.

To calculate the amount of ingredients needed for $$x$$ potions, you can use the expression $$y=\tfrac{73x}{81}$$, where $$x$$ is the amount of potions you want to make, and $$y$$ is the amount of raw materials you buy.

Players who have purchased the scroll and are making potions in large quantities may find it more efficient to withdraw 15 unfinished potions and 13 secondary ingredients each load, rather than 14 of each. Although, since the saved ingredients will need to be re-added to new potions, some prefer to just withdraw 14 of each, bank everything after making the potions and then repeat.

The following are not affected by the scroll:
 * Tea
 * Guam, Marrentill, Tarromin, and Harralander tars
 * Barbarian potions

Trivia

 * When this item was released, players quickly found that it did not affect all types of potions. On 1 February 2011, this problem was fixed as stated in the patch notes.
 * On the in-game Dungeoneering rewards guide, it is labeled by its original concept name, "Wasteless Herblore".
 * When a player buys this scroll from the Rewards Trader, it will appear on their Adventurer's log.
 * Unlocking the scroll of cleansing's ability is one of the requirements needed to get a trimmed Completionist cape.
 * When you save wyvern bonemeal, with the scroll of cleansing while making Super Prayer potions, it leaves an extra empty pot in your inventory or on the ground. The reason for this, is because the way the scroll is programmed, it does not technically save you an ingredient, simply adding an additional secondary ingredient of the same type to your inventory.
 * Once the scroll is read, it cannot be bought again. However, multiple scrolls may be bought as long as the ability hasn't been unlocked.
 * For some reason, the Scroll of cleansing does not save you the secondary ingredient when making Serum 207s, which in this case would be Ashes.