Jeff Malmer is a Senior Application Engineering Specialist for 3M. He has 40 years of product development and application engineering expertise and regularly trains 3M customers, end-users and sales professionals on proper use of the company’s products. Here, he tackles a common question he hears about spackling compounds.

Q: How do I know which type of spackling is best for my wall repair?

A: When it comes to spackle, you have two options—lightweight or a heavyweight product; the latter is also sometimes referred to as vinyl spackling.

With a heavyweight (vinyl) compound, you may be limited with the size of repair you can perform efficiently and effectively. Many pros still prefer heavyweight spackles because these products have been around longer and they’re more used to working with them. You’ll also hear some pros say heavyweight flows onto the surface better.

Some pros also opt for heavyweight spackle because they believe it is stronger than a lightweight product. But that’s not the case at all. In fact, many of today’s lightweight spackling products include 3M™ Glass Bubble technology. These ceramic bubbles strengthen the repair to withstand the impact of additional knocks and bumps after the job is done.

One significant downside to heavyweight spackle is that it tends to sag more, especially on vertical applications with large, deep holes. It’s also prone to shrinking once dry and may crack on larger repairs. For a larger hole, that means you may need to do extra fills, which requires more material and adds time to the job. If you find this is happening with your repairs, it may be time to switch to a lightweight option. Ideally, a heavyweight spackle should be limited to small dents, dings, and holes roughly the size of a pencil head.

A lightweight compound is far less likely to shrink or crack, and is recommended for holes up to about 3″ in diameter (about the size of a baseball or doorknob). Lightweight spackle dries faster, too. Most have a 20-30-minute dry time, whereas heavyweight products often require about twice that time. It’s also important to remember that these are recommendations based on tests done in a controlled lab environment. True dry times may vary, depending on the climate and repair size.

Since there are no absolutes with dry times, some pros also value a compound that’s easy to tell if it’s ready for sanding or not. Some like to start prep work in one area of a room; hoping that by the time they work their way around the room and back to the starting point, those first repairs will be dry enough for a quick sand, primer and paint. However, depending on the spackle you use and the temperature and humidity on the jobsite, you may need to factor in a little more time, especially for larger holes—even if you’re using a lightweight compound.

To make the sanding decision easier, you can also use a product like 3M’s High Strength Color Changing Spackling Compound. It goes on blue then transitions to white when the surface is ready for sanding. It makes the job easier for those crew members who might be new to the field; and even some long-time pros like to remove the guesswork from knowing when a repair is ready for sanding.

Whether you use a lightweight or heavyweight spackle, when the surface is ready, make sure to sand lightly with a medium-grit sandpaper while wearing appropriate respiratory protection. We recommend 180-grit, although you can go as low as 150 or as high as a 220-grit. And don’t forget, while many spackling products may indicate primer isn’t required, best practice is still to spot-prime the repair before painting.

To learn more about 3M spackling compounds, visit 3M.com/wallrepair