by Manuel Díaz de León

Manuel Díaz de León is a senior application engineer for 3M’s U.S. and Latin American markets. He has considerable expertise in wall repair, both as an engineer and avid DIYer, and provides extensive training and education for users around the world.

Q: Filler vs spackle: What are their pros, cons and best uses?

A: We hear this question often from both paint pros and DIYers. There are two specific angles to tackle when it comes to this answer: strength of the repair and dry time. Let’s talk about strength first.

Both filler and spackle are considered repair compounds that can take care of dents, nicks or holes in a wall. Spackle is primarily made with gypsum, with other compounds like concrete, primer or microglass beads sometimes added to improve strength; it is designed specifically for drywall. It will repair a hole, but many brands will only give you a fraction of the strength of the original drywall. If you try to penetrate the repaired area with a nail or screw, it will break down.

Spackle is easy to work with and dries white. It’s usually ready for primer and sanding the next day. Many spackles have primer in them, but not all do, so you need to double-check the label. Spackle is a common go-to for paint pros because it’s relatively inexpensive. That’s why you may commonly find spackle products such as 3M High Strength Small Hole Repair in a painter’s toolbox.

Filler provides significantly more strength for the repair. You also have the flexibility to fix a wider range of materials. You can tackle repairs on kitchen cabinets, metal doors, masonry, wood or steel railings, fiberglass, and more. And once dry, the repair is as strong as the original surface. When applied correctly, you can penetrate it with a nail or screw and it will hold up.

Dry time is the greatest differentiator between the two products.

In spackle, the binding particles join when the water finally leaves the mixture, allowing it to typically dry within one to 24 hours, depending on the size of the repair, air temperature and humidity. Filler, on the other hand, dries in only 15 to 30 minutes because it is made with polymers with a structure that is already intact, so you don’t need to wait for water to leave the compound.

As a paint pro, you may prefer the less-expensive spackle; filler’s price is usually about two to three times more than spackle. If you patch holes on the first day of a project, then the next day start masking and sanding the surface for painting, spackle will dry in time and serve you just fine. But sometimes when you are about to paint, you’ll notice a dent or hole you missed the previous day. Now you have a repair and can’t wait an additional day for it to dry. In those cases, filler can be used for the new repair and its fast dry time will help to keep your project on schedule. The fast dry time also minimizes concerns about sagging, which is a common problem with heavyweight spackle formulas, less so with lightweight ones.

Also, keep in mind that many fillers are two-part chemistry products where you have to mix a body formula with a hardener. There are also products such as 3M Bondo Glazing & Spot Putty, that are one-part chemistry types that require no mixing, and dry in about 30 minutes.

While some painters may be turned off by the cost of filler, it can be a valuable tool to have around for emergencies. And knowing it tackles repairs on most surfaces you encounter brings added peace of mind. You can use a high-quality spackle as your first choice, but it’s probably a good idea to keep filler in your toolbox for unexpected repairs or when you’re up against the clock. Remember that filler can save you time, which is a significant factor for your bottom line.

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