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Evidence Guide: CUVOPA05B - Complete pre-cutting processes for opal doublets and triplets

Student: __________________________________________________

Signature: _________________________________________________

Tips for gathering evidence to demonstrate your skills

The important thing to remember when gathering evidence is that the more evidence the better - that is, the more evidence you gather to demonstrate your skills, the more confident an assessor can be that you have learned the skills not just at one point in time, but are continuing to apply and develop those skills (as opposed to just learning for the test!). Furthermore, one piece of evidence that you collect will not usualy demonstrate all the required criteria for a unit of competency, whereas multiple overlapping pieces of evidence will usually do the trick!

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CUVOPA05B - Complete pre-cutting processes for opal doublets and triplets

What evidence can you provide to prove your understanding of each of the following citeria?

Select opal for cutting as an opal doublet or triplet.

  1. Select suitable materials for cutting as a doublet or a triplet based on market requirements and characteristics of the stone.
  2. Determine best play of colour and mark that side.
  3. Check for flaws with powerful light source and correct if necessary.
Select suitable materials for cutting as a doublet or a triplet based on market requirements and characteristics of the stone.

Completed
Date:

Teacher:		 Evidence:

 

 

 

 

 

 

 

Determine best play of colour and mark that side.

Completed
Date:

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Check for flaws with powerful light source and correct if necessary.

Completed
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Flatten opal and base.

  1. Flatten opal on marked side (this will be the best play of colour side) until surface is free of potch and impurities and completely down to the colour bar using appropriate equipment.
  2. Select backing materials and flatten.
  3. Lap opal and base until flat satin finish is obtained.
  4. Clean and dry opal and base.
Flatten opal on marked side (this will be the best play of colour side) until surface is free of potch and impurities and completely down to the colour bar using appropriate equipment.

Completed
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Select backing materials and flatten.

Completed
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Lap opal and base until flat satin finish is obtained.

Completed
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Clean and dry opal and base.

Completed
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Cement components together.

  1. Blacken flattened surface with appropriate blacking agent.
  2. Mix adhesive to manufacturers' instructions.
  3. Ensure stone is cemented with the best colour face down.
  4. Cement flattened surfaces together eliminating excess adhesiveness and air bubbles.
  5. Allow adhesive to harden following manufacturers' instructions.
Blacken flattened surface with appropriate blacking agent.

Completed
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Mix adhesive to manufacturers' instructions.

Completed
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Ensure stone is cemented with the best colour face down.

Completed
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Cement flattened surfaces together eliminating excess adhesiveness and air bubbles.

Completed
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Allow adhesive to harden following manufacturers' instructions.

Completed
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Preform opal doublet.

  1. Grind stone to expose join between opal and backing.
  2. Grind stone to expose best colour.
  3. Grind to rough shape.
Grind stone to expose join between opal and backing.

Completed
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Grind stone to expose best colour.

Completed
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Grind to rough shape.

Completed
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Convert doublet to triplet.

  1. When working with a very thin opal layer, manufacture a triplet.
  2. Lap the colour surface of the opal until a thin layer of opal remains on the backing.
  3. Clean and dry stone.
  4. Cement manufactured triplet top or preferred alternative to the opal surface eliminating excess adhesive and air bubbles.
  5. After curing, grind the stone to expose both joins.
When working with a very thin opal layer, manufacture a triplet.

Completed
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Lap the colour surface of the opal until a thin layer of opal remains on the backing.

Completed
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Clean and dry stone.

Completed
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Cement manufactured triplet top or preferred alternative to the opal surface eliminating excess adhesive and air bubbles.

Completed
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After curing, grind the stone to expose both joins.

Completed
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Follow OHS principles when operating machinery.

  1. Follow all general OHS principles and Safe Operating Procedures when using machinery for opal cutting.
Follow all general OHS principles and Safe Operating Procedures when using machinery for opal cutting.

Completed
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Assessed

Teacher: ___________________________________ Date: _________

Signature: ________________________________________________

Comments:

 

 

 

 

 

 

 

 

Instructions to Assessors

Evidence Guide

The evidence guide provides advice on assessment and must be read in conjunction with the performance criteria, required skills and knowledge, range statement and the Assessment Guidelines for the Training Package.

Critical aspects for assessment and evidence required to demonstrate competency in this unit

To achieve competency in this unit, a person must be able to select appropriate materials for making into a doublet or triplet and complete all pre-forming processes using safe working practices.

Assessment must confirm the ability to select the materials for making into a doublet and to make decisions on how to cut the material and what the final product should be. It involves preparing the opal and the backing material, flattening the stone and backing and cementing the two together. It also involves using the same skills to make a triplet from a very thin opal layer with a transparent triplet top.

Competence in this unit must be assessed over a period of time in order to ensure consistency of performance over the range of variables and contexts applicable to the work environment.

Context of and specific resources for assessment

This unit may be assessed in a work environment, in a simulated work environment or in a combination of these situations.

Method of assessment

For valid and reliable assessment of this unit, evidence should be gathered through a range of methods to indicate consistent performance.

Assessment of this unit of competence will usually include observation of processes and procedures, oral and/or written questioning on underpinning knowledge and skills, evaluation of the final product and other methods as required.

Assessment methods should closely reflect workplace demands (e.g. literacy) and the needs of particular groups (e.g. people with disabilities, and people who may have literacy or numeracy difficulties such as speakers of languages other than English, remote communities and those with interrupted schooling).

Assessment of this competency requires access to:

an opal cutting workshop

a qualified workplace assessor or assessment team.

Required Skills and Knowledge

Required skills:

use of appropriate equipment and consumables

ability to work safely with opal cutting equipment and materials.

Required knowledge:

the materials that are most suitable for making doublets or triplets

the equipment and consumables needed for making doublets and triplets.

Range Statement

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Suitable material may include:

multiple bars of colour with potch between

off-cuts from solid production

opal from unsuitable boulder iron stone

opal prone to crack (triplet only)

opalised shell skins

thin bar of colour in potch

thin seam opal

weak colour on a clear base (jelly opal).

Appropriate equipment may include:

diamond grinder

diamond saw

free-hand saw

silicon carbide grinder

slab saw

trim saw.

Backing materials may include:

black jade

black potch (best)

boulder iron stone

clear or transparent potch

dark grey potch

glass (triplet only)

obsidian (black)

vitrolite (triplet only).

Blacking agents may include:

black epoxy additives

black permanent markers

nigrosine.

Adhesives may include:

Loctite UV 358 or 363 (triplet top to opal)

UHU Plus 24hr (opal to backing)

other glues, such as UHU Quickset, MEGAPOXY 69, EPOXY 330, TENAX+ super glue, BOND 527, TITE ON.

Triplet top materials may include

clear quartz

commercial standards size triplet tops

glass, plain or plate

lead crystal glass

synthetic spinel, corundum, topaz.

General OHS principles and Safe Operating Procedures sheet may include:

complying with the safe operating procedures for each machine

good housekeeping

using personal protection equipment where required.