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Evidence Guide: CUVOPA205A - 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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CUVOPA205A - 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 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
  4. Follow general OHS principles and safe operating procedures when using machinery for opal cutting
Select suitable materials for cutting as a doublet or 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:

Teacher:
Evidence:

 

 

 

 

 

 

 

Check for flaws with powerful light source and correct if necessary

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Follow general OHS principles and safe operating procedures when using machinery for opal cutting

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Flatten opal and base

  1. Flatten opal on marked side until surface is free of potch and impurities and is 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 until surface is free of potch and impurities and is completely down to the colour bar using appropriate equipment

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Select backing materials and flatten

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Lap opal and base until flat satin finish is obtained

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Clean and dry opal and base

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Cement components together

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

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Mix adhesive in line with manufacturers’ instructions

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Ensure stone is cemented with the best colour face down

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Cement flattened surfaces together eliminating excess adhesive and air bubbles

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Allow adhesive to harden following manufacturers’ instructions

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Pre-form 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
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Grind stone to expose best colour

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Grind to rough shape

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Convert doublet to triplet

  1. Manufacture a triplet working with a very thin opal layer
  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
Manufacture a triplet working with a very thin opal layer

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

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

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

Clean and dry stone

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

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

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

After curing, grind the stone to expose both joins

Completed
Date:

Teacher:
Evidence:

 

 

 

 

 

 

 

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.

Overview of assessment

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

Evidence of the ability to:

select appropriate materials for making opal doublets and triplets

complete pre-cutting processes using safe work practices.

Context of and specific resources for assessment

Assessment must ensure access to an opal-cutting workshop with stones and equipment.

Method of assessment

A range of assessment methods should be used to assess practical skills and knowledge. The following examples are appropriate for this unit:

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

review of portfolios of evidence

review of third-party workplace reports of on-the-job performance by candidate.

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).

Guidance information for assessment

Holistic assessment with other units relevant to the industry sector workplace and job role is recommended.

Required Skills and Knowledge

Required skills

planning and organising skills to select and prepare opal backing materials for cutting

problem-solving skills to identify and address common problems associated with pre-cutting processes

numeracy skills to use numerical features of machinery

technical skills to:

complete pre-cutting processes for opal doublets and triplets using correct technique and equipment

work safely with opal-cutting equipment and materials.

Required knowledge

characteristics of opal gemstone structure

processes, materials and consumables needed for making doublets and triplets

safety issues associated with opal cutting and polishing machinery.

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 materials 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).

General OHS principles and safe operating procedures may include:

complying with the safe operating procedures for each machine

good housekeeping

using personal protective equipment (PPE) where required.

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

boulder iron stone

clear or transparent potch

dark grey potch

glass (triplet only)

obsidian (black)

vitrolite (triplet only).

Blacking agent may include:

black epoxy additives

black permanent markers

nigrosine.

Adhesive 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 may include:

clear quartz

commercial standards size triplet tops

glass, plain or plate

lead crystal glass

synthetic spinel, corundum and topaz.