Type of soldering for installing a zone valve

I purchased some honeywell zone valves and in there I found this notation:

"Sweat copper models, do not use silver solder because of the high melting temperatures required" Can someone tell me exactly what "silver solder" is? Is that a brand? What type of solder do I need to use in order not to damage this unit... I was surprised on the luck of information in the directions indicating what type of soldering I should be using.

I thank you in advance for your reply,

Steven

Potable water systems used to use a lead based solder...all new solder designed for potable water systems is silver based (i.e., silver solder) and not lead. So, since a heating system's water isn't used for drinking purposes, a lead based solder is okay, and, because it melts at a lower point than silver solder, is the preferred material when temperature is an issue. Now, where to find it is the harder issue. Maybe a good plumbing supply store.

I believe their referring to brazing rod, sometimes called silver solder. The 95/5 lead free should be fine.

i believe the instruction refer to remove the valve from the housing to eliminate any damage to ther valve during soldering. by the way, if you use mapp gas it is much hotter than propane which makes soldering very quick and easy

Silver soldering is brazing.

Standard soldering is done with tin. Most of the time it's in the 95% tin and a few other metals thrown.

Since this is for heating, you might be able to get by with 50/50 which is half lead and half tin.
I haven't carried any 50/50 in thirty eight years.
edited 2019

95% tin 5% antimony (what is 95 - 5 this was on a master plumbers test )

Then there is silver bearing solders and brazing alloys 15% silver no flux needed copper to copper

FYI the first number is the tin content such as 60 - 40 0r lead wiping Flemco #1 40 -60 I happen to like 38 - 42 as it stays molten longer for wiping