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Blue Stuff (also marketed as Oyumaru) is a reusable thermoplastic material for making small molds; it is not the material the duplicate is made from. Heat it according to its package instructions, press it against a suitable master, let it cool, then fill the impression with a separate material such as epoxy putty. It works best for a few copies of sturdy, shallow parts; complex undercuts and larger runs are better candidates for a purpose-made silicone mold.
For a first attempt, choose a part with a relatively flat or hidden back, such as a shield, badge, armor plate, or tile. Deeply enclosed shapes, fragile projections, and long parts may be difficult to release without damage or distortion.
What you need
- Reusable Blue Stuff molding material (Oyumaru is another search term for this type of material)
- Milliput epoxy putty or another suitable casting material, such as Maxx Putty or Magic Sculpt
- A clean, fully cured master part
- A heat-resistant container and water
- A utensil for handling softened material
- A hobby knife or sprue cutters for cleanup
- Small sculpting tools for pressing putty into details
Blue Stuff makes the mold, while the putty or other compatible material makes the copy. Follow the package instructions for the molding material and the casting material manufacturer’s instructions for mixing and curing.
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- Blue Stuff sticks is a new generation of thermoplastic molding material
- Reduced to mouldable conditions by immersion in hot water for 3 minutes
- REUSABLE plastic moulding for all levels.
- Dimension of each bar: 5.8x1.5x0.7cm
Choosing a mold method
| Approach | Best suited to | Things to consider |
|---|---|---|
| One-sided Blue Stuff impression | Shallow parts with a relatively flat or hidden back | Simple to make and release; putty can be pressed into the detailed face. |
| Two-part Blue Stuff mold | Parts with detail on both sides that cannot be copied as a shallow impression | Requires a planned parting line; seams, alignment, and trapped air can be problems. |
| Purpose-made silicone mold | Complex undercuts, larger production runs, or casting materials that may challenge a thermoplastic mold | Requires a different mold-making process; check material compatibility for the specific casting product. |
Which parts suit Blue Stuff?
Shallow parts with a clear direction of removal are the easiest starting point. Examples include shields, bucklers, armor plates, shoulder pads, pouches, badges, base decorations, and tiles. The key question is whether the master can leave the flexible mold without catching on deep recesses or fragile projections.
Long, deeply enclosed shapes and severe undercuts are poor candidates for a simple press mold. A community discussion about a long model-kit part cautions that such geometry may call for silicone; treat that as a practical warning, not a controlled comparison.
Rank #2
- Hobby Material
- When warmed, it cools softly and hardens, so it can be used as a simple mold material
- Use boiling water, so please be careful of scalds, etc
- Green StUFF World (Spain) Plastic Model Imported
Step-by-step: making and using a Blue Stuff mold
- Choose and prepare the master. Use a clean, fully cured part with sturdy details and a clear direction in which it can leave the mold. Thin blades, fragile projections, and severe undercuts may be damaged or trapped.
- Plan the impression. For a one-sided mold, place the detailed face against the softened material and leave the rear open. If the part needs a two-part mold, plan where the halves will meet and consider how the part will release before starting.
- Soften the material. Heat Blue Stuff in water according to its package instructions until pliable. The exact handling instructions depend on the product; do not rely on a universal time or temperature.
- Press it against the master. Press the softened material onto or around the part to capture the detail, while keeping enough material around the cavity to support it. Let the mold cool and set before removing the master.
- Fill the impression. Mix the epoxy putty according to its instructions. Press it into the detailed areas and then fill the rest of the cavity. Use a suitable tool to work putty into recesses.
- Wait for the cast to cure. Follow the casting material’s instructions; there is no universal cure time for all putties or cast shapes.
- Demold and finish. Flex the cooled mold away from the cured copy, then trim excess material or seams as needed. Reheat and reshape Blue Stuff according to its package instructions when reusing it.
Limits and troubleshooting
| Problem | Possible cause | What to try |
|---|---|---|
| Detail is missing | Putty did not reach a recess or the master did not release cleanly. | Press putty carefully into detailed areas and choose a master with manageable recesses. |
| Copy is distorted | The casting material was removed before it cured, or the mold flexed during filling. | Follow the putty maker’s cure instructions and make sure the mold is adequately supported. |
| Seam or mismatch on a two-part copy | The halves shifted or the parting line crossed a visible area. | Plan a stable parting line and align the halves carefully. |
| Master will not release | Undercuts or enclosed geometry have mechanically trapped it. | Do not force fragile parts; reconsider the mold split or use a different molding approach. |
| Resin affects the mold | The resin’s cure heat or chemistry may be incompatible. | Check compatibility for the specific resin and mold material. Consider silicone for demanding resin applications. |
Safety and responsible copying
Handle hot water and softened thermoplastic carefully, and follow the safety guidance supplied with epoxy putty or resin. Keep craft materials and tools away from food preparation and use appropriate ventilation and protective equipment as directed by the product maker.
Making a mold does not by itself grant permission to reproduce a design. Prefer your own work, public-domain material, or designs whose license permits copying. Check the relevant rights and permissions before distributing or selling copies of another creator’s work.
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Rank #3
- 【MIX RATIO 1A:1B BY VOLUME】no weighing scale necessary, this silicone mold making kit comes with 2 bottles, 2 gallon /17.6 lbs kit, part A 8.8 lbs, part B 8.8 lbs, very easy to use, also the bottle come with tinfoil sealed inside the cap, double guarantee for no leaking, a set of very helpful tools kiot will be included in the package: 20 pairs of disposable gloves, 10 mixing sticks, and 1 premium edge trim and 1 detailed user manual;
- 【SELF-DEGASSING & LOW VISCOSITY & EASY MIXING & POURING】this BBDINO 30A mold making silicone rubber has low viscosity so that you can easily mix and pour the silicone material, no degassing vaccum chamber needed, the molds finished with this liquid silicone for mold making has great flexibility & Strength. very easy to demold, Great silicone for mold making for simple one- or two-piece block molds making;
- 【WORKING TIME: 30 MINS, CURE TIME: 3~4 HRS AT ROOM TEMPERTUARE 25℃(73.4℉)】This pourable silicone for mold making cures at room temperature with negligible shrinkage, heat cure will shorten the cure time.
- 【LARGE VOLUME: 2 GALLON = 17.6 Lbs】PERFECT FOR ART AND INDUSTRIAL APPLICATION: BBDINO 30A mold making silicone rubber is a platinum grade additional silicone rubber mold making kit, which is widely used for mold making of arts crafts, like casting Resins, Wax, Gypsum, Concrete, Soap, Candle, and during making the silicone molds, no worries for contacting and touching, there will be no odor, no toxic, and no worry, the residues are very easy to clean by wiping off or peeling off after cured.
- 【LONG SHELF LIFE & VIVID COLOR】our BBDINO silicone rubber for mold making has a very long shelf life of over 1 year, you can easy save the rest materials for next time using by cover the cap back, no waste at all, and this mold making silicone 30A designed with a stunning Sapphire Blue Color, you can easily see whether part A and B mixed evenly enough and also you will make your arts and molds in a unique and beautiful Color!
Frequently Asked Questions
Is Blue Stuff the material used to make the copy?
No. Blue Stuff forms the mold. A separate material, such as epoxy putty, is pressed or poured into the impression to make the duplicate.
Can I use Blue Stuff for a long or deeply undercut part?
It may be difficult to release a long, enclosed shape or one with severe undercuts without trapping or damaging the master. Consider a different mold design or purpose-made silicone for complex geometry.
Rank #4
- Stays soft and does not dry out
- Easy to knead
- Gluten free and reusable
- Supports motor development
How long should the putty stay in the mold?
There is no universal time. Follow the instructions for the specific casting material and allow it to cure before demolding.
Can I cast resin in Blue Stuff?
Compatibility depends on the particular resin and conditions. Some resins can generate heat during curing, which may affect a thermoplastic mold. Verify compatibility for the products involved; silicone may be more suitable for demanding resin applications.
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Best Value
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Can Blue Stuff be reused?
Yes. It can be reheated and reshaped according to its package instructions. Check its condition before relying on it to capture fine detail.
Can I sell copies of a commercial miniature?
Do not assume that owning a physical miniature gives permission to reproduce its design. Check the applicable rights and license, and obtain permission where required.
The Bottom Line
Blue Stuff is a reusable option for a few small copies, especially from shallow, sturdy parts. Follow the product instructions, use a separate casting material such as epoxy putty, and allow that material to cure as directed. For severe undercuts, larger runs, or casting materials whose heat or chemistry may be unsuitable, consider a purpose-made silicone mold.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
