Soldering metals

Differences between soft solder and hard solder

Soft solder usually contains high amounts of soft metals like tin and lead.
The purpose of soft solder is to bridge a gap.
Hard solder connects two pieces of metal by expanding into the pores opened by high temperatures.
Hard solders are made of a high temperature metal (such as silver) with a small amount of tin to lower the melting temperature.
As long at a hard solder joint is protected with borax or yellow ochre, the melting point of the joint metal will rise with each successive heating.
Unlike hard solder, soft soldered joints become brittle with successive heatings. Also a soft soldered joint cannot be filed flush, because the strength of a soft soldered joint comes from the "encasing" of the joint ends by the solder.
Generally, hard solder forms a stronger joint than soft solder.

Hard solder

• What are the various grades of hard solder, their melting temperatures, and their precious metal contents?
  
  Most of the hard silver solders are a mixture of silver with copper and zinc. The temperatures are in degrees Celsius.
  
• SILVER SOLDER

• HARD GOLD SOLDERS
  

  A gold solder is usually an alloy which is a karat or more below the alloy it is actually used upon.
  For example, 12 karat yellow solder may actually contain only 10 karat gold, but it is meant for use with 12 karat gold.
  As a matter of fact, one does not need to use special solders with gold as a gold of a lower allow content may be used as solder.
  For example, ordinary 9 karat gold can be used to solder 12 karat,
  and 14 karat gold can be used to solder 18 karat gold.
  However, keep in mind that unlike silver solder, gold solder comes in a variety of colors and you should choose the right color solder with proper color of gold.
  
  

• I can't get my silver soldering to work. Can I use soft solder instead?
  

  Don't use soft solders. Some jewelers do use soft solder.
  A few have even been bold enough to admit it.
  There are several very good reasons not to use soft solder:

• Future jewelers will hate your guts. If a repair ever needs to be done, that future jeweler will get a very unpleasant surprise as he heats up the piece for hard soldering and have the whole piece fall apart because you took the easy way out!
• You decrease the precious metal percentage by adding significant amounts of soft, valueless metals.
• Most soft solders contain LEAD. Lead pits precious metals. Lead is toxic.
• Finally, the tin in soft solder destroys pickling solutions.

   DON'T USE SOFT SOLDERS!

• Do I need Easy-Flo solder?

  No. Easy-Flo solder was designed to be a lower melting alternative to Easy solder, and is often used in beginner jewelry making classes. Easy-Flo contains cadmium which is readily dissolved by pickling solutions, and when used with hot pickling solutions the cadmium can vaporize and be inhaled. Cadmium has a cumulative toxic effect, and has killed a number of jewelers.
  
  Maintainer Comment: I use only hard and medium solders and find them sufficient for all my needs. I like to discourage the use of Easy-Flo because it discourages proper soldering technique. Soldering is the most fundamental skill in silversmithing and proper technique should be taught from the beginning.
  
  

• Why isn't my silver solder working?
  
  

  Silver soldering is not an easy skill. It takes considerable patience and time to master. There are many reasons why a soldered joint cannot take. Below I present a small checklist of reasons why a soldered joint didn't work.
  
  

• A) Was the joint tight?
  
  

  Silver solder will not bridge across gaps like soft solder. The joint must be tight and flush. If you hold the joint up to the light and see light through it, it isn't tight enough. This is perhaps the hardest part of silver soldering.
  
  

• B) Is the joint clean?
  
  Grease, pickle, dust, charcoal, graphite, fire scale, and ochre will prevent solder from flowing into a joint. Clean your joints well. Fine sand paper will often do the trick followed by a rinse in water. Be careful with fingerprints.
  
  
• C) Did you use flux?
  
  Copper in alloys readily oxidizes forming fire scale which impedes solder flow. Using flux slows the fire scale formation. Before you solder a joint, cover the whole piece with flux. Flux also makes fire scale easier to remove in the pickling solution. You can also be generous with the flux since excess flux will simply burn off.
  
  
• D) Did you heat it fast enough?
  
  

  Heating must be done fast. If it isn't done quickly, the flux will burn off and fire scale will form. Buy the hottest torch you can afford.
  
  This is usually the greatest problem impeding soldering. The small butane or propane torch does not heat fast enough. Switch to a blow torch that uses MAP gas, or oxy/acetylene.
  
  

• E) Did you clean the solder before cutting it?
  
  

  Tarnish collects on silver solder, and if bad enough can impede flow.
  
  

• F) When you placed the solder on the joint, did it touch both sides of the joints?
  
  

  Solder does not flow according to gravity. It flows by capillary action and in the direction of the heat. If the solder is not touching both parts of the joint, when it liquifies, it will bead instead of flowing into the joint.
  
  

• G) Did you aim the torch on the solder itself?
  
  

  This is a big faux pas. Often though, a beginner (and even some experienced) smiths will become frustrated that the solder is not liquefying when the rest of the metal is red, and aim the torch right onto the solder. This, however, will burn out the lower temperature metals. The net result is that the soldier will have a higher melting point than the surrounding alloy, and you'll melt your base metals. Always remember, heat the joint NOT the solder.
  
  

• H) Did you pickle between solderings?
  
  

  Important. Pickle removes fire scale, flux, ochre, and other gunk. Pickle can be used hot or cold, but you must use it. And wash the pickle off, when finished.
  
  
  
  

What solders are appropriate for which metals?

   PICKLE

• My pickle covered my work with copper. What happened?
  

  Pickle works by the action of removing copper ions from a piece into the solution. If there are ions that are more readily taken into the solution, the pickle will deposit its excess copper ions onto your jewelry. Metallic contaminants include iron, tin, and zinc.
  To prevent pickle contamination, used wood, copper, or brass to remove items from the pickle, and refrain from using soft solder.
  
  

  
  
  
  
• What alloys of gold produce which colors?
  

  Gold alloys come in a variety of colors. Pure gold and alloys with a balance of metals are typically yellow. Other gold alloys include:
  
  

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