Potatoes Stick to Knife Blade

[dcarch]

--------------------  If you have a "fat" or wide bevel on your knife, you will need to exert a lot more force to slice a spud, since you are basically using a wedge to split apart the spud.  Multiple this force by 8-10 spuds and you'll want to go to a knife with a thinner bevel.....  

 

Not really.

 

The same splitting force is needed for a 10*/10* double bevel regular knife edge  as a 20* single bevel edge knife. That's the reason why I used a single bevel design.

 

dcarch

[daveb]

The splitting force required is not the sticking point here.  (Sorry - couldn't help myself)  Product sticking to the blade is.

 

Stickiness is a function of the product and is largely out of our control..  Sticktion is a function of blade design.  An inexpensive knife, the OP's VNox for example, will have a 50/50 bevel with a constant angle from bevel to spine.  Good for moving through product.  Bad for product sticking to blade (sticktion).  Certainly an adequate knife for most use and Mr. Kimball's current blade de jour. 

 

A more complex design will have a primary bevel at the edge and a secondary bevel moving up the blade.  This is the area of design trade-off.  A narrow secondary bevel will allow the knife to move through the product with less resistance but have more sticktion.  A wider bevel will hinder the knife moving through product but will hve less sticktion.  An aysymetric primary bevel is even more complex and will imrove both characteristics.  The design trade-off is done by the manufacturer and different customers will have different preferences.    There is no single right answer.

 

I did  watch the above video.  Am I the only one that could hear the blade chewing through the product?  A combination of poor technique and inappropriate desgn resulted in something that "slice" was never meant to describe.

[Norm Matthews]

Having a tool that helps slice a potato without it sticking is a solution to the original question but it does not really address why it sticks in the first place which is not really the question asked in the first place.  I wonder if the same knife would work on soft cheese or butter or does air pressure cause the same thing or does the properties of the substance contribute to the problem?  Why don't carrots or apples present the same problem?

[dcarch]

Having a tool that helps slice a potato without it sticking is a solution to the original question but it does not really address why it sticks in the first place which is not really the question asked in the first place.  I wonder if the same knife would work on soft cheese or butter or does air pressure cause the same thing or does the properties of the substance contribute to the problem?  Why don't carrots or apples present the same problem?

 

The most important thing is to clearly define the various different forces to avoid going in circles. For instance, adhesion is not suction. There is vertical force, horizontal force, dynamic pressure, static pressure, viscosity, etc. 

 

I am not sure why "sticktion" has anything to do with atmospheric pressure when it is so clear that in the case of using suction cups to climb a building, with no water or potatoes involved. I am not sure why it is not understood that our bodies are always pressurized from inside out to counter act 50,000 lbs of air pressure. Haven't you been in an airplane before with your ears popping? Seen astronauts in pressurized suits?

 

The case for cutting cheese is  a little different. Cheese happens to be a very good adhesive. To counter act air pressure and true adhesion, the cutter needs to be very minimal. A guitar cutter works well for cheese.

 

dcarch

[gfweb]

  Why don't carrots or apples present the same problem?

 

Carrots and apples are low suction. Potatoes are high suction. Cheese is very high suction.