Troubleshooting Leather Filler Application

Troubleshoot the following issues when applying Soft Filler repair putty on leather or vinyl upholstery.

Click any of the following:

Picture of peeling leather filler damaged by sanding

Why is Soft Filler peeling?

There are three possible reasons:

1. Sanding where the filler is thinly feathered on the perimeter of the repair.

Soft Filler adheres best to worn areas where suede or fabric (like a subpatch) are exposed. Where the filler overlaps and is thinly blended on finished or undamaged areas, it has less to grab, and care should be taken not to over-sand these areas.

The Solution: Be minimalist to avoid removing the resin completely and starting again (though this is okay too). Trim away any bulky peeling sections with nail scissors. Blend any peeling edges with rubbing or denatured alcohol. Allow to completely dry. Apply more filler, minimally, as needed. Avoid sanding and do a final texturizing coat to avoid a smooth, patched appearance.

2. The repair area has residue from other conditioners, furniture polish, or body oil.

The Solution: Perform the tape test near the repair area. If the tape doesn’t stick, neither will the filler. Clean thoroughly with denatured alcohol (or acetone as a last resort) to resolve the adhesion problem. Then re-repair using the suggestions for #1.

3. Filler was applied too thickly or is not fully cured.

Water in the filler evaporates in the curing process. The surface will skim over, giving the illusion that it’s dry. Applying more can then peel up the skimmed surface.

The Solution: Apply thinner layers. Ensure the filler is completely dry before applying more. Use an incandescent bulb or direct sunlight as a heat source to accelerate cure time. Hair dryers are not recommended, because they push moisture inward.

Why is Soft Filler still tacky?

Most often this is simply because the filler is not completely cured. Though technically an air-dry putty, it takes more than just a warm room to cure in a timely fashion. A heat source like an incandescent bulb, heat lamp or passive solar (sunny window) are needed to elevate the surface temperature to a range of 120º – 145º F (49º – 63º C). Hair dryers are not recommended, because they push moisture inward and prevent the water in the filler from evaporating.

Even with a heat source, it may take 20 minutes to a couple hours to cure, depending how thickly filler was applied. For this reason, thin layers are better than thick layers. Ensure the filler is completely cured and returned to room temperature before applying more.

Humidity is also a factor that can slow cure time.

If the filler remains tacky despite a proper heat source and sufficient time, it is usually remedied with the final texturizing coat of filler and a thin coat or two of our water-based color.

If not, then there are some other possible causes:

1. Residue from conditioner, body oil, or plasticizer is inhibiting the filler from curing.

Leather with oil stains may require extraction. Conditioner residue or a degrading urethane finish may also be the culprit. With vinyl, plasticizers can migrate outward and react with the filler.

The Solution: Make sure to clean the surface with denatured or rubbing alcohol prior to application of filler. Sometimes a more aggressive solvent like lacquer thinner is needed. Acetone can also be used with caution.

2. Adhesives used to subpatch any hole may not be dry and are preventing the filler from doing so.

The Solution: Wipe away uncured filler putty with alcohol. Ensure any glue used to subpatch has completely cured before proceeding. Letting it dry overnight is a good idea.

Why did Soft Filler dry with bubbles?

Bubbles in the cured resin are caused by too much heat. If you’re using an incandescent bulb, move it farther away from the repair area.

The Solution: Use a needle to poke a tiny hole in each bubble to allow it to deflate.

If the bubble lays down smoothly, apply a tiny bead of filler in the hole and smooth with your finger to seal it.

If the bubble did not lay down smoothly, try blending any peeling edges with denatured or rubbing alcohol. Acetone can also be used, but it will dramatically etch the filler, so be conservative. Allow to completely dry. Apply more filler, minimally, as needed. Avoid sanding and do a final texturizing coat to avoid a smooth, patched appearance.

Why did Soft Filler shrink after drying?

Shrinkage during the curing process is caused by applying the filler too thickly in any single layer and/or use of a hair dryer, which pushes moisture inward, rather than allowing it to evaporate with a radiant heat source (like sunshine or a light bulb).

The Solution: Apply thin layers of filler. Ensure it is completely cured before applying more. Use an incandescent bulb or sunlight to speed curing.


  1. Areas staying tacky to he touch. Filler rolls up when sanding. Working 5 areas. Two have repair patches and the other 3 were just cracks. All and areas were cleaned properly. I applied thin coats and have allowed days to dry. Have had light bulb for heat for hours. No direct sun light.

    • Tackiness means it needs more time to cure. Make sure the heat source is an incandescent bulb (not LED) or a heat lamp.
      Use alcohol to smooth imperfections if the sanding is creating issues.


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