Question: What addition to ketchup makes it flow more freely?
About the article "Ketchup", section "Viscosity".

Candidate passages:
The relatively high viscosity and pseudoplastic nature of ketchup can make pouring it from a glass bottle somewhat difficult and unpredictable, and several urban legends surrounding this phenomenon have arisen.
According to one popular folk remedy, repeatedly hitting the "57" mark on a glass Heinz ketchup bottle makes the ketchup pour out more quickly and easily.
The "New York Times" claims this is a matter of intentional design, with Heinz having placed the "57" mark on that particular spot of the bottle as a target for consumers to hit.
Whether or not Heinz intended the 57 as a target is unconfirmed; however, the effectiveness of this method of ketchup disbursement has been empirically confirmed as universally effective.
Simply hit the 57 firmly with the palm of your hand in order to free the flow of ketchup. 
Tomato ketchup has an additive, usually xanthan gum, which gives the condiment a pseudoplastic or "shear thinning" property.
This increases the viscosity of the ketchup considerably with a relatively small amount added - usually 0.5%.
- which can make it difficult to pour from a container.
However, the shear thinning property of the gum ensures that when a force is applied to the ketchup it will lower the viscosity enabling the sauce to flow.
A common method to getting ketchup out of the bottle involves inverting the bottle and shaking it or hitting the bottom with the heel of the hand, which causes the ketchup to flow rapidly.
A technique involves inverting the bottle and forcefully tapping its upper neck with two fingers (index and middle finger together).
Specifically, with a Heinz ketchup bottle, one taps the 57 circle on the neck.
This helps the ketchup flow by applying the correct shearing force.
These techniques work because of how pseudoplastic fluids behave: their viscosity (resistance to flow) decreases with increasing shear rate.
The faster the ketchup is sheared (by shaking or tapping the bottle), the more fluid it becomes.
After the shear is removed the ketchup thickens to its original viscosity.
Ketchup is a shear thinning fluid.
Shear thinning means that the fluid viscosity decreases with increasing shear stress.
In other words, fluid motion is initially difficult at slow rates of deformation, but will flow more freely at high rates. 
The relatively high viscosity and pseudoplastic nature of ketchup can make pouring it from a glass bottle somewhat difficult and unpredictable.
According to the Heinz trivia website ketchup exits the bottle at a speed of .
The website also notes that hitting the "57" mark on a glass Heinz ketchup bottle makes the ketchup pour out more quickly and easily.
The "New York Times" also notes that Heinz placed the "57" mark on that particular spot of the bottle as the best place for consumers to hit for the ketchup to pour smoothly.
The Heinz website claims that only 11% of consumers know this fact.
However, while the number "57" is used for the function of pouring, the number "57" resembles all the different types of products that the company offered.
The company actually manufactured 60 products when Henry Heinz introduced the number "57" on his ketchup bottles, Henry thought the number "57" was lucky and continues to use it today. 
Tourtière in Montreal is made with finely ground pork only (which can be hard to find as the meat is often ground too coarsely elsewhere).
Water is added to the meat after browning and the addition of cinnamon and cloves is what makes it unique.
Many people use ketchup as a condiment, though the tourtière is also often eaten with maple syrup or molasses, or mango chutney.
Although it is less popular than the original tourtière and the tourtière du Lac-Saint-Jean this version can also be commonly found throughout Canada and its surrounding areas.