Solder Not Melting? 5 Reasons Why This Might Be Happening

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Having problems with solder can slow your project or derail it altogether. If the solder doesn’t flow, the problems could begin to stack up fast. Practicing a few simple solutions will give you all the ammunition you need to stop a job from sliding out of control. It requires more work but makes a more solid weld. 

Soldering is useful for repairing metal objects but can be a pain if it doesn’t work correctly. Getting solder to flow correctly is something that takes time and practice to work out. However, even with years of experience, there can be hiccups and problems keeping solder from working. Don’t sweat it! Read on and learn five reasons why your solder isn’t working.

Cleaning Could be the Issue When Solder isn’t Melting

When it comes to clean surfaces for soldering, you should consider every surface involved in the process when cleaning. Foreign material in any part will mean that a bond could not be formed between the metal and the solder. Oil and dirt will create a barrier between the solder and the metal, which means that it won’t bond.

Cleaning the metal could be as simple as detergent and water or a complex as a wire brush on a drill bit. Take time to make sure it is spotless before moving on to the next steps. A clean surface is integral for soldering, and if you want to make a connection that lasts, the surface must be squeaky clean.

The things to clean when you are getting ready to solder are:

  • Metal – Clean the metal very thoroughly with a non-bleach abrasive and a small brush. Metal absorbs oil from your fingertips and dirt from workbenches and other pieces of metal. Working these oils and dirt out is imperative to this process. Run water across the metal after cleaning, and if there are no drops, it should be clean enough.
  • Solder – It might sound a bit crazy, but some solder can come dirty. It will have dirt and tiny particles that the naked eye can’t pick up. It is best to have a few scrub pads, the kind you do dishes with, and give them a quick scrub before heating the material. Small abrasions in the material also cause it to bond much easier.
  • Hands – Your hands are sometimes the culprit when the solder doesn’t melt. If you have been working and have dirty hands, bits of your grease and oil will rub off on whatever you are working with. Use a strong soap with a nice grit will remove all the oils and dirt from your hands.
  • Flux – Flux is another thing that could need some extra cleaning. If you have been using the same flux for a while, it can become contaminated by your brush. Ensure that you have decent brushes and that they are always cleaned before you begin any soldering process.
  • Workstation – Where you are doing your metalwork could be the dirtiest place in your entire shop; before the job starts, take the time to clean with a bit of soap and water. Once the area is free of dirt and oil, you should dry it with a towel that doesn’t have excess strings or fluff.

Working with metal and soldering is usually a dirty job. The dust from a grinder can be blown about in the wind like a sailboat on the open sea. Use the early stages to make sure that the locations and metals you use will be clean. Failure to clean the things will result in lousy soldering and failing pieces. Segregate pieces during working to keep them clean and ready. 

Heating the solder Appropriately is Another Reason it Might Not Flow.

Often when you are working with a torch, you could have the wrong amount of heat flowing to the tip. If this is the case, you won’t get more than a few solder drops around the location. Make sure that you have the right tools for the job when heating the solder. This is a trait that comes with experience and knowledge of the burner you are using.

The flip side of the heating problem is that some people could use too much heat. This heat could melt the solder and the metal you are working with; if the iron is hot, try and only hold it to the metal for a second or two at a time. If you can’t control the heat level, you can control the time that heat is on the metal. Find ways to be successful and fight through adversity. 

The most prominent ways to protect against melting metal are:

  • Practice – The most significant way to protect against having your solder melt away is practice. Over time you learn how to use the correct heat and which tip will work best for the job at hand. Use scrap pieces for training, and you will build confidence towards making more elaborate items.
  • Timing – The typical soldering iron will bridge gaps with the solder in about two seconds. Once you have some time down, it could be a one-second deal, but shoot for a two-second pulse to start. This protects the metal while allowing you time to decide if it is working or not. Pulsing is the most effective way to solder wiring. 
  • Iron Settings – Some soldering irons have a temperature setting that allows you to choose at what degree the soldering iron operates. Choose a setting that is appropriate for the metal and the type of solder that you are using. This will cut down on the melting incidents and save solder.

Practice Makes Perfect

Heat is essential to the soldering process. Try not to make each piece of metal you work with into an unworkable lump by overheating it. Overheating is fine when you are practicing but could be ruinous for a paid project. Always have extra pieces on hand because even the most skilled solderers can melt pieces sometimes.

Experience is a teacher that you should always listen to. Practicing gives you the knowledge that you can’t find from a web search or YouTube video. Use scrap pieces of metal before moving on to paying jobs. It is OK to melt a bit for fun; it is another thing when you ruin a client’s jewelry or clients plumbing. 

A Proper Fitting Could Make All the Difference

When you are working with metal, it has to be a tight fit for the solder to flow. If there are large gaps between the pieces of metal, you could be in trouble. The metal should be close enough that the solder doesn’t create the hole, just fills it. Also, a large gap will cause the metal to cool much faster, and heat and timing are essential when working with solder. 

If you are joining pieces of metal for a ring or fixing a spot of leaky plumbing, you must make sure that the pieces are correctly fitted. If not, there could be leaks, or the components could fail. If the solder has to make too much of a gap, it will not bond. Keep those pieces close together to ensure a tight fit.

Ways to ensure that there are no gaps in the metal are:

  • Use Clamps – Clamping pieces of metal together will free up your hands to use the solder and the iron at the same time. Place the clamps so that the metal is touching and only a sliver of space is allowed for the solder to fill. Using a clamp could lead to indentions in softer metals. Use padding when necessary.
  • Proper Sized Pipe – If you are working with plumbing, the problem could be finding the correct fit for the pipe size change. Often, plumbers will solder the cone-shaped pieces to fit the pipe. These fittings work because the solder forms a tight seal and contains water pressure that could be present in the pipework. 
  • Measure Correctly – Ensure that the pipes or pieces are the exact sizes you need will make gaps in the metal much smaller. Be sure that you have the correct measurements before setting anything that could have significant soldering done to it. Taking time to measure correctly will save time in the long run.

Having proper fittings is important for the solder to flow. If there is nowhere for the solder to go, it will stay on the iron tip. Solder is made for filling holes and not bridging gaps between pieces of metal. Only in specific art forms, like stained glass window making, will the solder be the connecting agent and not the filler.

It should be of no surprise that there will be metalwork for some soldering jobs. Be delicate with your metalwork and concentrate on leaving no marks on the metal. Make sure that you don’t damage any materials as you hammer and heat the metal parts. Too much heat or hammering could cause the metal to fail as soon as it goes into service.

A Heat Sink Could be the Source of Solder Flowing Problems

Another reason that solder could have a problem flowing is that something is robbing its heat. A heat sink is a name given to a metal object, usually steel, that takes away heat from the objects you are trying to solder. Metal like steel can take several hundred-degree temperatures before it begins to melt. Solder melts at much cooler temps.

When working with computers, heat sinks are a critical part of soldering and wiring circuit boards. A heat sink is laid on the weld or solder path, and it keeps the precious material underneath from melting. Melted soldering parts will destroy sensitive welds and links on a circuit board that could house important fans or critical CPUs.

The best products to use for a heat sink are:

  • Elenco ST-23 HeatsinkThe typical way to get a heat sink while working with electronics is to have an alligator clip. These clips will need to be located by the solder location and absorb any excess heat that could damage the circuit. Be quick with your work, as too much heat will ruin it.
  • Marame Gel Cloth – An alternative to the alligator clip is the gel cloth. It absorbs a massive amount of heat and can be molded to any shape that you could need. Be careful as the fabric is so spongy that you could bend pieces that reside under it. Pieces can also be cut down for small jobs.
  • Goot Heat Clip – Another great clip heat sink is the pair made by Goot. They can work in a combo to bring down specific parts of the board that are sensitive to heat. Often if a circuit board has attached fans or CPUs, it could need several heat sinks to give it adequate protection. 

A heat sink will make the solder refuse to melt off of the spool. You should check each metal piece and what they are connected to before you begin working. A heat sink in computer work operates much differently and protects the board from being fried when used at high temperatures.

Sometimes a heat sink could be hard to find. Use something to scuff the metal to see what type it is. Steel will be able to take much more heat than tin or copper. A piece of steel also works well as a heat sink to keep heat away from sensitive circuitry or electric components when you are soldering. 

Flux is Another Thing to Check if your solder isn’t Flowing Well.

Flux does some fantastic things to metal and is a determining factor in how well solder attaches to metal. There are several different kinds of flux, and they can be thought of as a kind of metal paste. This metal paste helps heated metal accept solder and protects it from overheating, and some types even let you know when it has gotten too hot.

Flux works by reducing surface tension on the metal. Surface tension is one of the main reasons that solder won’t flow when soldering. Excess tension also means that the solder will not hold on to the metal. Instead, it will begin to pool around the edges or run away from the site altogether. Watch the heat as flux can change colors when it is too hot and fail to work correctly.

A few ways to make flux work better for soldering are:

  • Temperature Gauge – Some types of flux can be used to determine how hot the soldering iron is. When it reaches a specific temperature, it will become see-through and give you a better view of the metal. This is essential information for the younger solder wielders and provides them excellent training.
  • Buy Appropriate Flux – Not all flux will work with all types of metal. There are specific flux types used for each type of metal. Take that into consideration when choosing metal and flux; they must be compatible. All are made from rosin that helps bonding agents remove any imperfections in the solder. 
  • Watch the Temperature – Some flux will stop working when it gets too hot. They have a temperature ceiling, around 1700 degrees, that once reached, they will no longer have the glue-like properties that it is used for. Check the label on your flux before starting the job to avoid any injuries or mishaps while working on the metal. 

The main job of flux is to reduce surface tension on the metal. It can come in a powder or a paste form, and both should be used liberally when you are soldering. The main thing that flux does is fill tiny holes in the solder or weld that would usually be missed. Use a large amount of flux as it cannot hurt soldering until it becomes too hot.

Flux is used in all types of hot metalwork to act as a sticking agent. This ‘metal glue’ comes in a powder form that can be sprinkled on the work surface. Once sprinkled, it bonds metal agents together like glue and will aid in bridging those tiny gaps in the solder. Use as much or as little as you need; flux is cheap and cannot permanently damage the metal you are working on.


Solder is a substance that can be used in all different types of industry. In construction, it is used to seal pipes, and in electronics, it can be used to attach electrical pieces to sensitive circuitry. Solder can have a difficult time flowing if you use too much heat or fail to heat the metal surfaces you are working on adequately.

When solder isn’t flowing correctly, there are a few things that you can do to get back to work. Check the heat of the soldering iron. Too much heat will liquefy the solder and the metal you are working on. Use time as a means to control the heat—close gaps in the metal. Solder is for filling holes, not gaps in metalwork.

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