How to Choose CA Glue: A Guide for Wood, Stone and Models

GUIDE · ADHESIVES

How to Choose CA Glue: A Guide for Wood, Stone and Models

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Choose CA glue by the width of the joint: thin glue wicks into hairline cracks and tight-fitting joints, medium handles both, and thick fills gaps up to 0.5 mm without running. An accelerator helps when you need the bond instantly or you are gluing a porous material.

How do you choose a CA glue that holds the first time? This guide walks through three decisions in the order you make them at the workbench – and for wood repairs it adds color, so the joint blends into the grain.

01How to choose CA glue: three questions that decide

Look at the joint first, not at the glue. Thickness decides whether the glue gets into the joint or stays in it.

• How wide is the gap? Parts fit tightly → thin. A gap you can see with the naked eye → thick.
• What are you gluing? Porous wood and ceramics soak up glue, ordinary CA glue dissolves foam, and polyethylene and polypropylene do not bond at all.
• How much time do you need? The fastest thin glue grabs in a few seconds; slower and thicker glues give you half a minute to align the parts.

All glues sorted from the thinnest to the thickest are in the thickness overview in one place.

02Thickness made simple: water, oil, syrup, honey

Thickness (viscosity) is given in centipoise – cPs. Water is about 1, honey around 2,000. The lower the number, the more the glue flows and wicks into seams; the higher it is, the more it holds its shape and fills.

What is the difference between thin and thick CA glue?

Thin glue (2–40 cPs) draws itself into a tight seam by capillary action – you apply it to parts that are already fitted together or into a crack, not into a gap. It is also used to stabilize fragile wood and stone. Medium (150 cPs) flows into gaps up to 0.15 mm wide and fills small gaps at the same time. Medium-thick (500 cPs, like syrup) fills more than it flows. Thick (2,000 cPs) fills a 0.25–0.5 mm gap and does not run even off a sloped or vertical surface.

Thickness does not tell the whole story about speed, though. The fastest is the thin EM-02 (2–5 seconds), medium EM-150 grabs in 10–15 seconds and thick EM-2000 in 20–30 seconds. Thin Original Super Thin and EM-40 also take 20–30 seconds – on purpose, so there is time to spread them when finishing.

If you are not sure, start with medium

Medium thickness does a bit of everything – it flows in and it fills. Add thin and thick later, once you know you need them:

EM-150 Mediumall-rounder for most jobs · 150 cPs · sets in 10–15 sView › EM-02 Super Fast Thincracks, tight joints, stabilizing · 2–3 cPs · 2–5 sView › EM-2000 Gap-Fillerknots, gaps, sloped surfaces · 2,000 cPs · 20–30 sView ›

The glues come as a Pro Kit: with the bottle you get micro-tips for precise dosing, a cap with a pin that keeps the nozzle from clogging, and a spare nozzle.

03Which CA glue for which material

CA glue bonds wood, metal, ceramics, stone, rubber, leather, laminate and most plastics – the difference is in the thickness and in what to watch out for.

Which CA glue for wood?

Thin for consolidating soft or punky wood and for hairline cracks, medium for gluing parts and small repairs, thick for knots, voids and loose joints. If the repair should disappear into the grain, choose a colored glue to match the species (chapter 05).

Which thin glue for a CA finish on the lathe?

Three clear thin glues suit a glossy protective coat on turned pens, bowls and handles. EM-02 sets the fastest, so the coats build up the fastest. Original Super Thin gives you 20–30 seconds to spread it and has a low tendency to bloom. EM-40 is slightly thicker (40 cPs), spreads less and leaves fewer stains around the joint on light wood.

Original Super ThinCA finish, stabilizing · 2–5 cPs · 20–30 s to spreadView › EM-40 Heavy Thinfinish, cracks, inlays · 40 cPs · clear bond without hazeView ›

For stone, minerals and fossils

Thin glue soaks into cracked stone and consolidates it; it is also used in fossil preparation and for inlays made with metallic powders. Medium is enough to glue a crystal to wood – it stays clear after curing.

For metal and ceramics

Medium or thick glue. Lightly roughen smooth metal before gluing; unglazed ceramics soak up part of the glue.

For plastics and 3D prints

Thin glue bonds PLA, ABS, PETG and polycarbonate prints as long as the parts fit precisely. Loose fits and layers with gaps are better filled with thick glue. With a new plastic, always test the bond in a hidden spot.

Does CA glue bond polystyrene?

Ordinary CA glue dissolves foam. For foam models, balsa structures and work where a strong odor is a problem, NO-05 Odorless was designed – a very thin glue made from a different type of cyanoacrylate (2-methoxyethyl), foam-safe and low in odor. You still need to ventilate.

NO-05 Odorless
foam-safe · low odor · 4–7 cPs›

What CA glue does not work on

Polyethylene (PE), polypropylene (PP) and silicone. These materials have such low surface energy that the glue cannot grip them – you will recognize them by their greasy, waxy surface (jerry cans, food containers, silicone molds).

04What an accelerator does and why CA glue blooms

An accelerator (also called an activator) is a solvent-based product that triggers the reaction of CA glue instantly. Without it, the glue cures with moisture from the air – quickly in a thin layer, much more slowly in a larger amount or in a gap.

• instant fixing – the parts hold the moment you put them together; handy for batch gluing,
• stops soaking in – on balsa, softwood and ceramics it stops thin glue before it disappears into the material,
• colored fills – black KE-150 and KBL-500 take 1–2 minutes to set without an accelerator and about 20 seconds with one; for filling knots and cracks the maker of the colored glues recommends it,
• primer for difficult surfaces – applied to one side of the joint before gluing, or sprayed over the glue once it is applied.

Why CA glue blooms and how to prevent it

The white haze around a joint (blooming) forms mainly with too much glue and slow curing: vapors escape from a large drop and settle on the surrounding surface as a white film. The best prevention is a small drop and parts pressed tightly together. A thick layer of glue in the middle also does not cure all the way through, and the joint is weaker.

05Black, brown and flexible CA glues

Clear glue in dark walnut or wenge stays visible as a light line. Colored CA glues hide the repair – choose them by the color of the wood and by whether you are filling a crack or a knot.

KE-150 Black Medium flows into fine cracks in dark wood, KBL-500 Black Medium-Thick fills knots and voids up to 0.2 mm. For light wood there is BR-150 Light Brown, for walnut BR-500 Dark Brown.

• the black glues are rubber-toughened – they handle impact and vibration better, but set more slowly, in 1–2 minutes,
• the brown ones set in 20–30 seconds; build up a larger fill in layers,
• after curing, sand the repair flush and polish it; black KE-150 takes stain, oil and lacquer,
• also handy for small repairs when sanding epoxy tables and boards.

Flexible glue for rubber, leather and vibration

Ordinary CA glue is hard and brittle once cured – it cracks on impact or when flexed. KEG-500 Flexible (500 cPs, clear) is rubber-toughened and handles impact and vibration better. Use it on rubber, leather, metal-to-rubber joints, shoe soles, rubber tool grips and arrows. It gives you 20–30 seconds to align the parts.

06CA glue or epoxy? When CA glue is not enough

CA glue is the master of thin joints. As soon as the gap is wider than half a millimeter, the joint carries a load or you need minutes to assemble, reach for a two-part epoxy.

For a missing piece of material there is epoxy putty – you model it and sand it once cured.

5-Minute Epoxy Kitfast two-part adhesive · workshop repairsView › 30-Minute Toughened Epoxytough, absorbs shocks · 30–35 min working timeView › Wood Epoxy Puttywood putty · replaces a missing pieceView › Concrete Epoxy Puttyputty for concrete, masonry · stoneView ›

The full range of two-part adhesives and putties is in the epoxy adhesives category.

07Make it last: storage and safe work

CA glue ages from the same moisture that cures it – on a warm windowsill with the nozzle open it thickens within a few weeks.

1. Store it cold – ideally in a fridge at 4.5 °C or below, tightly closed. For most glues the manufacturer then states a shelf life of 30 months.
2. Let the bottle warm up before work to room temperature, so moisture does not condense inside.
3. Dose with a micro-tip – the drop will be exactly as big as you need, and the nozzle will not clog.
4. After work, push the pin from the cap into the nozzle and close the bottle right away.

Related products and categories

• All-rounder: EM-150 Medium · Thin: EM-02 · Thick: EM-2000
• CA finish: Original Super Thin, EM-40 · Foam and low odor: NO-05
• Black: KE-150, KBL-500 · Brown: BR-150, BR-500 · Flexible: KEG-500
• Clear range: transparent CA glues

Related guides

• Starbond adhesives overview
• How to make an epoxy resin table – repairing knots with CA glue before pouring

Frequently asked questions about CA glue