The difference between spackle and joint compound can be so subtle that it effectively becomes non-existent to the layperson. It is unlikely to even be immediately apparent to anyone that doesn't work in the renovating or decorating industry, but knowing more about these can ensure that you pick the right material for your future projects.
The word 'spackle' has gone from being just a trademark name owned by the Muralo Company to a generic word for any substance on the market that fills holes in walls. It was originally produced in powder form, which needed to be mixed with water in order to be used. It is now also available in a ready-made paste.
Joint compound is a substance that is actually often referred to as 'drywall mud' and is of a similar consistency to plaster.
Spackle made up from the powder must be used as soon as it has been mixed together with water to prevent it from drying out and becoming too hard to use. Both this and the ready-made type are prone to quickly drying out if left exposed to air. To prevent waste when using the powder form, only use as much as is necessary for the job at hand.
Although joint compound is also capable of drying out, it will take longer to do so than spackle when left exposed to the air.
Both substances should be stored in an airtight container when not in use.
Spackle is ideal for household use, making it easy to repair small holes in plaster or drywall, such as those made by nails that were hammered into the wall. It can be applied with a flexible spatula and any excess scraped away before it's left to dry. If the surface doesn't appear completely smooth, it should be gently wiped with a damp sponge. After it has dried, it can be treated like any other part of the wall and will withstand sandpaper, paint, and wallpaper.
Joint compound is often used alongside drywall or gypsum boards to cover the joints between the panels, and other larger jobs. It essentially acts as a mask; several coats need to be applied to cover blemishes, fasteners or screws. Similar to spackle, joint compound can also be used to repair larger holes that require a backing to help hold the repairing substance, such as a mesh, in place. Overall, joint compound is usually meant for larger projects that require more durability.
Though it depends on where you go, spackle is usually more expensive than joint compound. They are both widely available and can be found relatively cheap if you're prepared to shop around or in bulk.
Spackle comes in different consistencies, which are known as grains, and vary between heavy and light. The one you choose depends on the task it is to be used for. Small jobs, such as filling nail holes and minor depressions, will only require the light version. It is prudent to be aware of the various types before making a purchase so that you can be sure what you buy is capable of the job.
Joint compound comes in many consistencies as well, some heavier and some lighter, as well as a few different forms, like a pre-mixed compound or a powder to mix with water for the quick-setting variety.