A great question and one that needs expounding upon.

‘Waxy’ potatoes are a loose definition for variety, or non-russet potatoes – which are lower in solids.

Russet potatoes are higher in solids.

All potatoes by the way are measured primarily in solids. The simplest way to describe potato solids is the percentage of potato starch vs the water content within.

To compare and contrast: Most fresh produce items are 90-plus percent water such as lettuce or melons, for example. Idaho russet Burbanks in comparison, measure in at a consistent 79% water content and 21% solids. This explains why when you fry or steam mushrooms or kale, its volume reduces considerably when cooked. The Idaho russet potato after baking as you know, retains much of its volume and finishes as a wonderful, dry and fluffy product – ready for your favorite toppings to enjoy.

To get back on the waxy topic…Potatoes such as reds, long whites or yellow types (aka Yukon golds for example) are among the waxy varieties and are designated so due to their higher water content. This trait makes them especially conducive for recipes calling for higher-moisture performance or for the eye appeal that a purple, red or mixed color skin-on provides - such as in potato salads or as roasted potatoes.

These waxy varieties are generally sized as ‘A’ (about the size of a tennis ball or slightly larger, ‘B’ size (roughly the size of a racquetball), and the ‘C’ or creamer size is about the size of a ping-pong ball or smaller. Russet potatoes in contrast, are sized according to approximately how many fit into a 50# carton: 40 in a 40 ct, 50 in a 50 ct all the way up to 120 in a 120 ct carton.

Here are a few links that should be helpful:

https://idahopotato.com/dr-potato/qa-test-for-high-solids-content-in-potatoes.

https://idahopotato.comhttps://cdn.idahopotato.com/uploads/media/red-yellow-potato-size-guide.pdf

https://idahopotato.com/foodservice/cost-and-size