Knowledge Forum

1. First, Why Choose Magnesium Oxide Cement for DIY?

Before diving into the process, let’s highlight the key advantages of magnesium oxide cement:

1. Easy to Shape: It has good fluidity, fitting various molds perfectly—even for complex textures.

2. Low Cost: Raw materials are budget-friendly; around $15 buys enough to make 3-5 medium flower pots.

3. Eco-Friendly & Durable: Formaldehyde-free, with high hardness (reaching 80% of traditional cement strength after curing). It’s also waterproof and mildew-resistant, making it suitable for outdoor use.

4. Lightweight: 30%-50% lighter than traditional cement, so it’s easier to carry and place.

Ideal DIY projects: Small flower pots, storage boxes, decorative ornaments, and small coffee table tops. Beginners should start with simple, small items!

2. DIY Prep: Beginner-Friendly Material & Tool List

No complex equipment needed—everyday tools plus basic materials are all you require:

2.1 Core Materials (for 1 medium flower pot)

2.2 Tools (Affordable—under $20 online if you don’t have them)

• Mixing Tools: Electric mixer (for efficiency) or manual mixing stick + plastic basin

• Measuring Tools: Digital scale (accurate to 1g), Baumé hydrometer (tests magnesium chloride concentration), measuring cup

• Molds: Silicone molds (easiest for demolding, great for complex shapes), PVC molds, wooden molds (requires release agent)

• Protective Gear: Dust mask, acid/alkali-resistant gloves, safety goggles (magnesium oxide powder is dusty; magnesium chloride is slightly corrosive)

• Auxiliary Tools: Scraper (smoothes surfaces), small brush (applies release agent), sponge (retains moisture during curing)

3. Key Steps: From Mixing to Demolding (Don’t Skip Any!)

Step 1: Prepare Magnesium Chloride Solution (Key! Concentration Determines Strength)

This is critical—too high concentration causes cracking; too low leads to soft, uncured products.

1. Crush 200g of magnesium chloride flakes and place them in a plastic basin (never metal—they corrode).

2. Add 150ml of tap water and stir until flakes fully dissolve. Control water temperature at 20-30℃ (too cold slows dissolution; too hot disrupts reactions).

3. Test concentration with a Baumé hydrometer—25-28 Baumé degrees is optimal:

◦ Too low: Add a small amount of extra flakes.

◦ Too high: Add a little water, stir, and retest until 达标.

1. For coloring: Add inorganic pigments now and stir until the color is uniform. Don’t add too much—this reduces hardness!

Step 2: Mix Magnesium Oxide Powder & Aggregate

1. Weigh 500g of magnesium oxide powder and 300g of aggregate (quartz sand/vermiculite) into another plastic basin.

2. Stir them evenly with a mixing stick to avoid clumping. Crush any lumps by hand if needed.

Step 3: Mix the Slurry (Goal: No Lumps + Thick Paste Consistency)

1. Slowly pour the prepared magnesium chloride solution (with pigment, if using) into the powder-aggregate mixture—stir while pouring.

2. Mix manually for 5-8 minutes, or 1-2 minutes with an electric mixer, until the slurry meets two standards:

◦ No dry powder lumps (lumps cause rough surfaces or holes).

◦ Thick paste consistency (when lifted with a stick, it drips slowly—neither too thin nor too dry).

✅ Pro Tip: If the slurry is too dry, add ~10ml of magnesium chloride solution. If too thin, add a small amount of magnesium oxide powder—DO NOT add water!

Step 4: Pour into Molds (Removing Air Bubbles = Smooth Surfaces)

1. First, use a small brush to apply a uniform layer of release agent to the mold’s inner walls—focus on corners to prevent sticking.

2. Pour the slurry slowly into the mold, filling it to 80% capacity (prevents overflow and leaves room for shrinkage).

3. Remove air bubbles: Gently tap the mold’s sides (or flick with your fingers) to make bubbles rise and burst. For deep molds, insert chopsticks into the slurry and stir a few times to release trapped air (unremoved bubbles cause dents or holes).

4. Smooth the surface: Use a scraper to level the slurry at the mold’s top. Fill any gaps with excess slurry.

Step 5: Curing (Patience = No Cracks!)

Magnesium oxide cement doesn’t need watering—temperature control + moisture retention are key. Poor curing causes cracking!

1. Initial Setting: Place the mold in a ventilated, shaded area (optimal temperature: 15-25℃). Avoid direct sunlight or wind. Let it sit for 24 hours to partially cure.

2. Moisture Curing: After 24 hours, the surface should no longer feel sticky. Gently wipe it with a damp sponge (or wrap the mold in plastic wrap with a few air holes) to retain moisture. Wipe 1-2 times daily for 7 days.

❌ Mistakes to Avoid: Direct watering (washes away surface components); placing near air conditioners/heaters (low humidity causes cracking).

Step 6: Demolding & Post-Processing

1. After 7 days of curing: Gently pull the mold’s edges (silicone molds can be folded directly). Slowly remove the product. If stuck, use a knife to cut along the gap—don’t force it!

2. Post-Demolding Curing: Place the product in a ventilated area for another 2-3 days to boost hardness.

3. Post-Processing: Sand minor defects gently with sandpaper. For a smoother finish, apply a layer of transparent protective paint (water-based paint is best—eco-friendly).