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How to Choose and Apply the Best Wood Filler for Balsa Wood Repair

You've spent hours meticulously carving your balsa masterpiece, only to watch a heavy, clunky wood filler shrink and crack the delicate grain or turn your feather-light model into a weighted paperweight. It's incredibly frustrating when a patch job ruins the structural integrity or leaves an ugly, visible scar on such soft timber, but you don't have to settle for a finish that compromises your hard work. By choosing a specialized, ultra-lightweight putty, you ensure your repairs sand down as smoothly as the wood itself, keeping your project agile and looking flawless once the final coat is applied. Getting that seamless, professional look is easier than you think, especially once you discover why some of the most effective solutions aren't the traditional pastes you'd expect to find on a hardware store shelf.

How to Choose and Apply the Best Wood Filler for Balsa Wood Repair
Deluxe Materials Model Lite Balsa Filler

Deluxe Materials Model Lite Balsa Filler

  1. Weight Density: Ultra-lightweight formula designed specifically not to add significant mass to model aircraft.
  2. Sanding Compatibility: Sands easily and at the same rate as soft balsa wood to ensure a flush finish.
  3. Shrinkage Resistance: Formulated to dry without shrinking, cracking, or pulling away from the edges.
  4. Material Base: Water-based, non-solvent, and low-odor for safe indoor use and easy cleanup.
  5. Best for: Filling gaps, grain, and surface imperfections in lightweight balsa wood models and RC planes.

Gorilla All-Purpose Wood Filler

Gorilla All-Purpose Wood Filler

  1. Dry Time: Approximately 15–30 minutes for shallow cracks.
  2. Usage Versatility: Suitable for both interior and exterior applications.
  3. Material Stability: Highly resistant to shrinking and cracking after curing.
  4. Surface Finish: Exceptional sandability that allows for a smooth, paintable, and stainable surface.
  5. Best for: Lightweight model building and seamless balsa wood repairs.

BONCART Paintable and Stainable Wood Repair Putty

BONCART Paintable and Stainable Wood Repair Putty

  1. Material Formula: Water-based, eco-friendly composition.
  2. Surface Compatibility: Fully paintable and stainable finish for seamless blending.
  3. Physical Stability: Non-shrinking and crack-resistant properties after curing.
  4. Workability: Fast-drying texture that is exceptionally easy to sand.
  5. Best for: Lightweight balsa wood modeling and delicate hobby craft repairs.

Bondo All-Purpose White Plastic Filler

Bondo All-Purpose White Plastic Filler

  1. Two-Part Formula: High-strength resin and hardener system that ensures a permanent, non-shrinking bond.
  2. Cure Speed: Fast-acting chemical reaction that is ready to sand in approximately 20 to 30 minutes.
  3. Finish Color: Bright white, non-staining appearance that provides a clean base for paint or primers.
  4. Material Compatibility: Versatile adhesion properties designed for use on wood, metal, masonry, and plastics.
  5. Best for: Structural repairs and filling deep gouges in balsa wood hobby models and RC aircraft.

SEISSO Wood Filler Putty Repair Kit

SEISSO Wood Filler Putty Repair Kit

  1. Formulation Base: Water-based, non-toxic, and eco-friendly composition.
  2. Finishing Capabilities: Highly paintable and stainable to match surrounding wood grain.
  3. Drying Performance: Fast-drying formula designed to resist shrinking and cracking.
  4. Application Texture: Smooth, easy-to-spread consistency that requires minimal sanding.
  5. Best for: Lightweight balsa wood aircraft models and delicate hobby crafts.

J-B Weld QuikWood Epoxy Putty Stick

J-B Weld QuikWood Epoxy Putty Stick

  1. Work Life: 15 to 25 minutes.
  2. Full Functional Cure: 60 minutes.
  3. Material Stability: Non-shrinking, non-cracking, and solvent-free.
  4. Post-Cure Versatility: Can be sanded, drilled, sawed, planed, and painted.
  5. Best for: High-strength structural repairs and filling large gouges in lightweight balsa wood models.

Minwax Wood Putty, Golden Oak, 3.75-Ounce

Minwax Wood Putty, Golden Oak, 3.75-Ounce

  1. Non-Hardening Formula: Stays flexible and does not dry hard to accommodate natural wood movement.
  2. Container Size: 3.75-ounce pre-mixed jar.
  3. Color Matching: Color-matched to Minwax Wood Finish stains for seamless blending.
  4. Post-Finish Application: Designed to be applied after staining and top-coating with no sanding required.
  5. Best for: Filling small nail holes and minor cosmetic gaps in finished balsa wood models and crafts.

Stainable Wood Filler Putty

Stainable Wood Filler Putty

  1. Material Composition: Water-based, non-toxic formula with low odor.
  2. Drying Time: Fast-drying, typically sandable within 30 to 60 minutes for shallow repairs.
  3. Finish Compatibility: Fully paintable and stainable to match surrounding wood surfaces.
  4. Structural Integrity: High resistance to shrinking, cracking, or crumbling once cured.
  5. Best for: Lightweight balsa wood models, craft projects, and delicate furniture repairs.

Roberts Wood & Laminate Putty Repair Kit

Roberts Wood & Laminate Putty Repair Kit

  1. Formula Base: Water-based acrylic for low odor and easy water cleanup.
  2. Drying Time: Fast-drying formula designed for quick-turnaround repairs.
  3. Material Compatibility: Versatile adhesion for wood, laminate, vinyl, and tile surfaces.
  4. Post-Application Processing: Fully sandable and paintable once cured to ensure a seamless finish.
  5. Best for: Filling small cracks and surface imperfections in lightweight balsa wood models and hobby crafts.

DAP Plastic Wood-X Wood Filler with DryDex Technology

DAP Plastic Wood-X Wood Filler with DryDex Technology

  1. Dry Time Indicator: Goes on pink and dries to a natural finish when ready to sand.
  2. Surface Finishing: High-performance formula that can be sanded, planed, drilled, painted, or stained.
  3. Structural Integrity: Provides a hard, durable finish that is shrink and crack resistant.
  4. Application Versatility: Formulated for both interior and exterior use with easy water clean-up.
  5. Best for: Filling small cracks and surface imperfections in lightweight balsa wood models.

Old Masters Natural Wood Putty 3.75 oz.

Old Masters Natural Wood Putty 3.75 oz.

  1. Material Formula: Non-hardening, oil-based composition.
  2. Product Volume: 1/2 Pint (approx. 8 oz).
  3. Color Profile: Natural wood tone (intermixable with other colors).
  4. Application Method: Press into hole and wipe away excess; no sanding required.
  5. Best for: Filling small nail holes and cracks in pre-finished balsa wood models and woodworking projects.

Goodfilla Water-Based Wood Grain Filler

Goodfilla Water-Based Wood Grain Filler

  1. Formulation Base: Water-based, non-toxic, and zero VOC content.
  2. Shrinkage Resistance: High-solids formula that is guaranteed not to shrink, sink, or crack.
  3. Shelf Life: Unlimited lifespan as the product can be easily reconstituted with water if it dries out.
  4. Finish Compatibility: Accepts any stain, paint, or clear coat without ghosting or clogging sandpaper.
  5. Best for: Filling grain and repairing surface imperfections in lightweight balsa wood models and hobby crafts.

System Three SculpWood Putty (2-Gallon Kit)

System Three SculpWood Putty (2-Gallon Kit)

  1. Mixing Ratio: 1:1 simple volume ratio of resin and hardener.
  2. Cure Time: Sets to a sandable state in approximately 24 hours.
  3. Density: Lightweight, wood-like consistency that mimics softwoods.
  4. Shrinkage: 100% solids formula with zero shrinkage or cracking after application.
  5. Best for: Large-scale structural repairs and filling deep voids in porous balsa wood.

12-Piece Wood Filler and Repair Kit

12-Piece Wood Filler and Repair Kit

  1. Formulation Type: Water-based, non-toxic, and low-odor composition.
  2. Finish Compatibility: Fully paintable and stainable once completely dry.
  3. Drying Time: Rapid-setting formula designed for quick sanding and finishing.
  4. Included Accessories: Comprehensive kit featuring 2 scrapers and 3 pieces of sandpaper.
  5. Best for: Lightweight balsa wood repairs and hobbyist model building.

ElectricWise Moldable Silicone Putty Glue (4-Pack)

ElectricWise Moldable Silicone Putty Glue (4-Pack)

  1. Full Curing Duration: 24 hours to reach maximum bond strength.
  2. Temperature Resistance Range: -50°C to +150°C (-58°F to +302°F).
  3. Environmental Protection: 100% waterproof, weatherproof, and UV-resistant.
  4. Working Window: 30 minutes of moldable time for precision shaping.
  5. Best for: seamless gap filling and structural reinforcements in lightweight balsa wood models.

Deluxe Materials Model Lite Balsa Filler

Deluxe Materials Model Lite Balsa Filler

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Ever feel like one accidental gouge just ruined your hours of careful balsa carving? Don't sweat it, because Model Lite Balsa Filler is the ultimate fix for those frustrating gaps that threaten your perfect build. You're finishing a delicate wing and spot a seam, but instead of using heavy traditional putty, you apply this ultra-lightweight formula that fills deep holes without adding a single gram of unnecessary weight to your flight. It dries fast. It sands like a dream. Because it is water-based, cleanup is effortless, ensuring your model maintains a seamless, professional finish that looks like the mistake never happened. No stress. No weight. Just perfection.

Gorilla All-Purpose Wood Filler

Gorilla All-Purpose Wood Filler

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Stop struggling with those annoying gaps and dings that ruin the delicate finish of your balsa wood projects, because Gorilla All Purpose Wood Filler is the ultimate smooth-fix solution you've been looking for. This high-performance formula is specially designed to be shrink and crack-resistant, meaning your repairs stay flush and professional-looking even on lightweight, porous wood. Since it's incredibly easy to sand, paint, and stain, you'll get a seamless match that makes imperfections disappear without any extra hassle or heavy lifting. Whether you're perfecting a model airplane or a craft masterpiece, this filler gives you the durable, high-quality surface your hard work deserves. Grab a tub now and make your next project flawless!

BONCART Paintable and Stainable Wood Repair Putty

BONCART Paintable and Stainable Wood Repair Putty

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We've all been there-you're putting the final touches on your balsa masterpiece only to spot a glaring gouge or a messy gap that ruins the vibe. Stop stressing and grab this BONCART wood filler to make those eyesores disappear like magic. Just clean the area, squeeze a bit of this creamy putty into the crack, and level it off with a scraper so it's nice and flush. Since it's a high-density, water-based formula, it won't shrink or crack on you, saving you from the frustration of double-work. Once it dries, give it a light sand and go ahead with your paint or stain; it blends so perfectly that no one will ever know there was a flaw. You get a rock-hard finish that stays put, giving your delicate balsa projects the professional, seamless look they deserve without the usual cleanup headache.

Bondo All-Purpose White Plastic Filler

Bondo All-Purpose White Plastic Filler

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Tired of seeing tiny gaps and surface nicks ruin the smooth lines of your balsa wood masterpiece? This specialized wood filler is the ultimate solution, designed to bridge those imperfections so you can get back to the fun part of your build. Its fast-drying, lightweight formula means you can sand it down to a perfect feather-edge in minutes without putting any stress on fragile ribs or sheeting. Because it bonds tightly and accepts paint flawlessly, your repairs will be completely invisible once you apply your final finish, giving you that professional, competition-ready look every time. Stop struggling with rough surfaces and pick up a tube to perfect your model today!

SEISSO Wood Filler Putty Repair Kit

SEISSO Wood Filler Putty Repair Kit

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Working with balsa wood is a delicate balancing act, and nothing ruins your flow like an unexpected crack or a messy gap in your model. You need a solution that's as lightweight as your project, which is why SEISSO Water-Based Wood Filler is your new best friend for achieving that seamless finish. Its smooth, water-based formula means you get a professional-grade fill that won't shrink or crack, allowing you to sand, stain, or paint your balsa wood until it looks absolutely perfect. Because it dries quickly and cleans up with just water, you can spend less time worrying about repairs and more time perfecting your craft. Grab your tube now and make those imperfections disappear!

J-B Weld QuikWood Epoxy Putty Stick

J-B Weld QuikWood Epoxy Putty Stick

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Stop stressing over those annoying gouges and gaps that keep ruining your balsa wood models, because this QuikWood epoxy putty is the ultimate fix for your crafting headaches. You just cut off a small chunk, knead it with your fingers until the color is uniform, and press it firmly into the damaged area; it's basically like a magic "undo" button for your mistakes. Because it's specially formulated to be non-shrinking and cures in just 15 to 25 minutes, you won't have to deal with unsightly cracks or long wait times before getting back to work. Once it hardens, you can sand it down to a seamless finish, drill it, or paint it to blend perfectly with your build, giving you a professional-grade repair that's actually stronger than the original wood. It's the easiest way to turn a structural nightmare into a smooth, paint-ready surface without the mess of runny glues or the frustration of shrinking fillers.

Minwax Wood Putty, Golden Oak, 3.75-Ounce

Minwax Wood Putty, Golden Oak, 3.75-Ounce

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We've all been there: you've spent hours meticulously crafting a balsa wood model only to find a glaring nail hole or a nasty little gap that ruins the whole aesthetic. Instead of letting a minor flaw wreck your hard work, grab this Minwax Wood Putty to make those imperfections disappear in a snap. Because it's a non-hardening formula, it won't shrink or crack your delicate balsa fibers over time, meaning your project stays looking fresh without the risk of the filler popping out as the wood settles. To get a seamless fix, just clean the area, press a bit of putty into the hole with your fingertip, and wipe away the excess with a damp cloth-it's a total no-brainer since there's absolutely no sanding or drying time needed. Since it comes pre-tinted to match your wood perfectly, you're saving yourself the messy trial-and-error of staining, giving you a professional, color-matched finish that lets your craftsmanship take center stage.

Stainable Wood Filler Putty

Stainable Wood Filler Putty

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You've spent hours meticulously crafting your balsa model only to spot a frustrating crack or a clumsy gouge, but don't sweat it because this wood putty is the ultimate wingman for your delicate projects. It tackles those imperfections head-on with a shrink-resistant formula, meaning you won't have to waste time re-filling the same hole twice. To get your build back on track, just clear away any dust, press the putty firmly into the defect with a knife, let it quick-dry, and sand it smooth to a seamless finish. Since it's specifically engineered to be ultra-lightweight and porous, it takes paint and stain just like real wood, giving you a professional, invisible repair that keeps your masterpiece looking flawless.

Roberts Wood & Laminate Putty Repair Kit

Roberts Wood & Laminate Putty Repair Kit

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Ever notice how one tiny nick in your balsa wood project can ruin the whole vibe? You're pouring hours into a masterpiece, but those stubborn gaps and dents just won't quit. Grab this ultra-lightweight wood putty and watch those flaws disappear. Since it's specially formulated to match balsa's delicate density, it sands down effortlessly without gouging the surrounding wood. This means you get a seamless, feather-light finish that takes paint perfectly. No more heavy patches. Just smooth results. Fix it fast. Finish it right. You've got this.

DAP Plastic Wood-X Wood Filler with DryDex Technology

DAP Plastic Wood-X Wood Filler with DryDex Technology

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If you're tired of seeing ugly gouges and seams ruin the sleek lines of your balsa model or craft, this wood putty is the secret weapon you've been looking for. We know how frustrating it is to guess if your filler is dry, but this smart formula goes on pink and turns natural when it's ready to sand, saving you from accidental smears and wasted time. Because it's reinforced with real wood fibers, it grips those delicate balsa pores for a professional-grade bond that's easy to sand smooth without crumbling or tearing the wood. You'll get a seamless, rock-hard finish that takes stain and paint perfectly, making your hard work look absolutely flawless. Grab your tub today and finish your build like a pro!

Old Masters Natural Wood Putty 3.75 oz.

Old Masters Natural Wood Putty 3.75 oz.

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You've spent hours meticulously sanding your balsa model, only to spot a glaring crack that threatens the whole build. Don't let a small gap ruin your hard work. Most heavy fillers are too brittle for soft wood, but this wood putty is the pro-grade solution you need. Because it's non-shrinking, your repair stays flush with the surface for a seamless, professional look. It sands effortlessly, ensuring you don't damage the delicate surrounding fibers during cleanup. It accepts stain and paint perfectly. No visible scars. Total precision. Apply. Dry. Sand. Perfection.

Goodfilla Water-Based Wood Grain Filler

Goodfilla Water-Based Wood Grain Filler

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Tired of your balsa models looking more like a dry sponge than a sleek masterpiece? We've all been there, watching your hard-earned paint job disappear into those pesky open grains, but Goodfilla is the ultimate secret sauce to stop that frustration in its tracks. Just schmear a thin layer of this creamy filler over your wood, scrape off the excess with a plastic spreader, and give it a quick sand once it's dry to reveal a surface that's finally as smooth as glass. Because this high-solids formula is designed not to shrink, sink, or crack, you won't have to waste time doing the same job twice, and since it's water-based and non-toxic, you get a pro-level finish without the nasty fumes or a messy cleanup.

System Three SculpWood Putty (2-Gallon Kit)

System Three SculpWood Putty (2-Gallon Kit)

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Dealing with those annoying gouges and fragile cracks in your balsa wood projects can feel like a losing battle, but SculpWood is here to save your hard work. This two-part epoxy putty acts just like modeling clay, allowing you to fill gaps and rebuild missing sections without the frustration of shrinkage or cracking as it cures. You get a permanent, sandable surface that's actually tougher than the original wood, ensuring your model planes and delicate crafts look flawless and stay structural for years to come. Since it won't sag or run, you can finally stop stressing over imperfections and get back to the creative parts of your hobby. Grab your kit now and finish your masterpiece!

12-Piece Wood Filler and Repair Kit

12-Piece Wood Filler and Repair Kit

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Hey there, if you've been hunting for the absolute best way to patch your delicate balsa projects, you have finally found the ultimate solution with this professional-grade wood putty. This water-based formula is engineered with a high-solid density that ensures a shrink-resistant cure, meaning you get a rock-solid repair that won't crack or fall out over time. Because the mixture is exceptionally fine-textured and paintable, you can effortlessly sand it down to a seamless finish that blends invisibly with your wood grain for the most flawless results imaginable. You'll love how the quick-dry technology saves you hours of waiting, while the included precision scrapers and sandpaper provide everything you need for the most pristine restoration possible. It is quite simply the most effective and user-friendly kit on the market, giving your balsa wood the superior, long-lasting durability it deserves.

ElectricWise Moldable Silicone Putty Glue (4-Pack)

ElectricWise Moldable Silicone Putty Glue (4-Pack)

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Stop stressing over those annoying gouges and gaps in your balsa wood model that make your hard work look like a DIY disaster; ElectricWise Moldable Wood Putty is the secret weapon you need to get that flawless finish without the headache. To fix your frame, just wipe away any dust, press a small amount of the putty directly into the crack with your finger or a putty knife, and smooth it over until it's flush. Because it's engineered to be ultra-lightweight, it won't mess with your RC plane's flight balance, and its heat-resistant, waterproof formula means your repairs stay rock-solid even when things get messy or hot outside. Once it hardens up in no time, give it a quick sand and you'll see it blends right in, giving you a professional, seamless surface that's ready for paint or covering.


Best types of wood putty for ultra-lightweight balsa wood

Choosing the right filler for balsa wood requires a balance between weight and sandability. Standard hardware store putties are often too dense, creating "hard spots" that make sanding difficult without gouging the surrounding soft wood.

  • Microballoons mixed with resin: Extremely light, ideal for non-structural gaps.
  • Vinyl-based lightweight spackle: Often called "modeler's lite filler," it offers the best weight-to-volume ratio.
  • Balsa-tinted water-based putty: Provides a natural look for clear-coated projects.

Solving structural integrity issues with balsa wood fillers

While most fillers are cosmetic, structural repairs require compounds that bond deep into the fibrous grain of balsa. When structural integrity is compromised, the filler must act as a bridge between the fractured cells.

Issue Recommended Filler Type
Cracked Spars Epoxy resin with milled glass fibers
Crushed Leading Edges Cyanoacrylate (CA) and balsa dust paste
Loose Rib Joints Thixotropic wood glue mixture

How to match balsa grain and density with filler compounds

The goal of matching balsa is to ensure the filler responds to sandpaper at the same rate as the wood. If the filler is too hard, you will sand away the balsa around it, leaving a high spot. To achieve a perfect match, many builders create a custom paste using sanding dust harvested from the same sheet of balsa being repaired, mixed with a drop of clear dope or diluted white glue.

Preventing shrinkage and cracking in large volume balsa repairs

Large repairs are prone to "dishing," where the filler shrinks as it cures, leaving a concave surface. To prevent this, apply the filler in multiple thin layers rather than one thick application. For deep voids, use "scabs" or small off-cuts of actual balsa wood to fill 80% of the volume, using the putty only as a surface leveler. This technique significantly reduces the chemical shrinkage and prevents internal stress cracks from forming over time.

Water-based vs solvent-based putty for RC model balsa builds

The choice between water and solvent bases often depends on the intended finish. Water-based putties are generally lighter and easier to clean, but they can swell balsa fibers if applied too heavily. Solvent-based putties dry faster and do not cause grain raise, but they can be brittle and may react negatively with certain foam-core components found in hybrid RC models.

Techniques for sanding balsa wood putty without damaging soft grain

Balsa is exceptionally soft, making it easy to over-sand. Use these techniques to maintain surface flatress:

  1. Use a long sanding block to bridge across the repair onto the surrounding wood.
  2. Start with 220-grit paper; anything coarser will tear balsa fibers.
  3. Apply "witness marks" with a soft pencil across the repair; stop sanding the moment the marks on the wood disappear.
  4. Always sand with the grain to avoid cross-grain scratches that show through under film.

Achieving seamless surface prep for heat-shrink films and paint

Heat-shrink films like Monokote or Oracover will highlight every imperfection. The filler must be sanded flush and then vacuumed to remove all dust from the pores. If the filler is too porous, the film adhesive will not grab. A light coat of "sanding sealer" over the filled area ensures a uniform surface tension, preventing bubbles when the heat gun is applied to the film covering.

Weight-sensitive filler application for aerodynamic balsa components

In high-performance gliders or indoor flyers, every gram matters. To minimize weight, use the "dry-fill" method. Press dry microballoons into a crack and wick in a tiny amount of thin CA glue. This creates a solid, ultra-light bridge. Always weigh the component before and after filling to ensure the Center of Gravity (CG) has not shifted beyond acceptable limits for flight stability.

Chemical compatibility between balsa putty and cyanoacrylate glues

Many modelers use CA glue to harden filler or speed up repairs. However, some lightweight spackles contain vinyl or moisture that can cause CA to "kick" instantly, creating a charred, brittle mess. Always test a scrap piece first. If using a water-based filler, ensure it is 100% dry before applying CA, or the trapped moisture will cause the glue to turn opaque white and lose its bonding strength.

Hardening agents for reinforcing soft balsa edges with wood putty

Balsa edges on trailing surfaces or wingtips are prone to "mushing." You can create a "hard edge" by mixing wood putty with a hardening agent.

  • Thin CA: Wicking thin glue into the putty creates a plastic-like durability.
  • Baking Soda: Mixing with CA creates an instant-cure, rock-hard filler for high-stress corners.
  • Clear Dope: Mixing filler with aircraft dope provides a flexible yet resilient edge that resists dings during transport.


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Marcus Thorne brings over 15 years of experience in executive search and corporate headhunting to Covlett.
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