Craftwork
Senior 3 · Fine Arts
Craftwork
Lesson 3 of 4
25 min
Look closely at the toy car below, made by learners at a school in Namibia. Its frame is bent wire. Its body panels are cardboard, painted blue, and they are held to the frame not with glue but with dozens of tiny wire stitches along every edge. The wheels came from old toys and are fixed on an axle. Glue alone would never have held cardboard to bare wire. Choosing the right join for each pair of materials is what makes a recycled object strong enough to be used and not just looked at.
Definition
Mechanical join: a join held by shape or by a fixing, such as a slot, a stitch, a screw or a twist of wire. It can often be taken apart.
Adhesive join: a join held by glue.
Tab: a small flap that fits into a slot or is glued to another surface. Flange: a strip folded along an edge to give a gluing surface.
Temporary join: one that can be undone, such as tape or a paper fastener. Permanent join: one that is not meant to come apart.
| Join | How to make it | Best for | Permanent? |
|---|---|---|---|
| Tab and slot | cut a slot just wider than the card is thick; push the tab through and fold it flat | card, thin plastic | fairly; can be undone |
| Glued flange | fold a 1 cm strip along the edge and glue it to the next piece | card boxes and frames | yes |
| Cross-halving | cut a slot halfway into each piece; push them together | card stands and dividers | no; slides apart |
| Lacing or stitching | punch holes at equal spacing; stitch with string, raffia, wire or plastic strips | card, fabric, plastic, rubber | yes, and decorative |
| Paper fastener | push a split pin through both layers and open the legs behind | moving parts, such as wheels or arms | no; it pivots |
| Wire twist | wrap wire round both parts several times; twist the ends with pliers and tuck them in | wire frames, sticks, handles | yes |
| Screw and washer | make a pilot hole; screw through a washer so the screw does not pull through | caps, cans, plastic onto wood | yes, and removable |
| Plait and knot | plait three strips; finish with a firm knot | fabric strips, plastic bags, fibre | yes |
| Adhesive | Good for | Care |
|---|---|---|
| PVA (white glue) | paper, card, fabric, wood | slow to dry: hold or clamp the join; weak on plastic and metal |
| Flour paste (home-made) | paper and papier mâché | for paper only; can go mouldy if left damp |
| Contact adhesive | rubber, leather, some plastics | strong fumes: use only with the teacher, in a well-ventilated room |
| Hot-melt glue gun | quick joins on card, fabric and some plastics | the nozzle and glue cause burns; use with supervision |
| Tape | holding parts while glue dries; temporary trials | peels with time; not a final join |
Many smooth plastics, such as drink bottles, do not glue well. For them, and wherever a join must carry weight, use a mechanical join or combine both: glue for neatness and a stitch, screw or wire for strength. Always test a join on scrap pieces first.
Worked example 1: spacing lacing holes
Kaneza will lace two pieces of carton together along an edge 30 cm long, with a hole every 1.5 cm, starting and ending at the corners. How many holes does each piece need?
Gaps: gaps between holes.
Holes: one more than the gaps, because there is a hole at each end: holes in each piece.
Mark all the holes with a ruler before punching, so the stitches are even.
Worked example 2: choosing a join
Nkurunziza wants to fix a plastic-bottle scoop to a wooden handle for a garden tool. PVA failed: the scoop came off the next day. What should he do?
Diagnosis. PVA does not grip smooth plastic, and the join carries a load every time soil is lifted.
Solution. Use a mechanical join: drill two small holes through the bottle neck and the handle and fix it with two short screws and washers, or bind the neck tightly to the handle with several turns of wire, twisted and tucked in.
<em>5 Minute Demo: Cardboard Attachment Techniques</em>, from Big Ideas Art Studio. Count the different joins shown and match each one to a row in the table above.
Warning
Punching and cutting. Punch holes into a scrap board, never towards your hand. Use a craft knife only with the teacher, with a cutting mat and a metal ruler.
Glue safety. Use hot glue and contact adhesive only under supervision, in a ventilated room, and keep them away from your face.
Tip
Glue for neat, mechanical for strong. Where a join must carry weight or bend, add a stitch, a screw or a twist of wire.
Practice
What is the difference between a mechanical join and an adhesive join? Give an example of each.
Which join would you use for a wheel that must turn on a card toy? Explain.
Why is PVA a poor choice for joining two plastic bottles?
An edge 24 cm long is to be laced with holes every 2 cm, with a hole at each end. How many holes are needed in each piece?
For a cross-halving join, two pieces of card are each 12 cm tall. How deep should each slot be?
Analyse the wire car in the photograph: name two joins the makers used and explain why each suits its materials.
Join test. Make three different joins between your chosen materials on scrap pieces. Test each by pulling and bending, record what happened, and choose the joins for your craft object.
1. A mechanical join is held by shape or a fixing (for example tab and slot, wire twist, screw); an adhesive join is held by glue (for example PVA on card).
2. A paper fastener (split pin): its legs hold the wheel on while letting it pivot.
3. PVA does not grip smooth plastic, so the join peels apart; use a mechanical join or a suitable plastic adhesive.
4. gaps, so holes.
5. Half the height: each.
6. Wire stitching joins the cardboard panels to the wire frame, since glue cannot hold card to bare wire and the stitches flex without tearing; bent and twisted wire joins the frame parts, which makes a strong, light skeleton. (The wheels are fixed on an axle so they can turn.)
7. Check: three joins tested on scraps, results recorded, and choices explained by the materials and the load.
Which join surprised you most in your tests, by being stronger or weaker than you expected? How will that change your plan?
Sources and credits
