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Activity 002: Acid Cream Etching with Vinyl Resist

Activity ID: U12M4-ACT-002 Duration: 40 minutes

Overview

Students apply a vinyl resist stencil to glass, apply commercial etching cream, and produce a frosted design. This activity teaches the complete chemical etching workflow: surface preparation, resist application, cream application, timing, rinsing, and cleanup — with strong emphasis on chemical safety and proper PPE throughout.

Materials & Equipment Needed

  • Flat glass pieces (soda-lime, 4" x 6" or similar) — one per student
  • Commercial glass etching cream (e.g., Armour Etch or equivalent)
  • Vinyl resist film (self-adhesive, pre-cut stencil designs or blank sheets for hand-cutting)
  • Vinyl cutter (if creating custom stencils) or pre-cut stencil designs
  • Transfer tape (for positioning cut vinyl designs)
  • Craft knife and cutting mat (for hand-cutting resist)
  • Squeegee or plastic card (for burnishing vinyl)
  • Chemical-resistant gloves (neoprene or butyl rubber — NOT standard nitrile)
  • Safety glasses or chemical splash goggles
  • Disposable plastic applicator brushes (foam brushes)
  • Plastic tray or container for etching (to contain cream and rinse water)
  • Running water source for rinsing
  • Paper towels
  • Isopropyl alcohol (for glass cleaning)
  • Calcium gluconate gel (must be present and accessible — HF antidote)
  • Timer
  • Ventilation (open window or fume hood — etching cream releases mild fumes)
  • Hazardous waste container for used cream and rinse water

Instructions & Procedure

Part 1: Safety Briefing and PPE (5 minutes)

  1. Instructor delivers mandatory safety briefing before any materials are distributed:
  2. Etching cream contains bifluoride compounds that release hydrofluoric acid slowly
  3. Skin contact causes irritation and potential chemical burns — delayed onset
  4. Chemical-resistant gloves (neoprene/butyl rubber) are mandatory — standard nitrile is insufficient
  5. Safety glasses/splash goggles are mandatory
  6. Calcium gluconate gel location is identified — this is the specific antidote for fluoride burns
  7. If cream contacts skin: rinse immediately with water for 5 minutes, then apply calcium gluconate
  8. Students don PPE: chemical-resistant gloves and safety glasses/goggles
  9. Instructor verifies all students are properly equipped before proceeding

Part 2: Surface Preparation and Resist Application (10 minutes)

  1. Clean glass thoroughly with isopropyl alcohol — fingerprints cause uneven etching
  2. Dry completely
  3. Apply vinyl resist stencil to the glass:
  4. For pre-cut stencils: use transfer tape to position, then peel transfer tape away
  5. For hand-cut designs: apply vinyl sheet to glass, then cut design with craft knife on the glass surface
  6. Burnish the resist firmly with squeegee or plastic card:
  7. Press all edges thoroughly — cream will seep under poorly adhered resist
  8. Check for bubbles or lifted corners — press down
  9. Remove the center sections of the design (the areas to be etched), leaving the border/protect areas covered

Part 3: Etching Cream Application (15 minutes)

  1. Place the prepared glass piece in the plastic tray (catches drips and rinse water)
  2. Apply a thick, even layer of etching cream over the exposed glass areas:
  3. Use a disposable foam brush
  4. Apply generously — thin application produces uneven results
  5. Ensure complete coverage of all exposed glass within the stencil openings
  6. Do not brush back and forth repeatedly — apply in one smooth coat
  7. Set timer for the recommended duration (typically 5-10 minutes per manufacturer's instructions)
  8. During the wait:
  9. Do NOT touch the cream or the piece
  10. Do NOT lean over the piece (avoid breathing fumes)
  11. Instructor leads discussion on acid etching chemistry vs. mechanical etching
  12. When timer expires, rinse the piece under running water:
  13. Hold glass at an angle so cream runs off into the plastic tray
  14. Rinse thoroughly — all cream must be removed
  15. Continue rinsing for at least 30 seconds after cream appears to be gone

Part 4: Resist Removal and Evaluation (10 minutes)

  1. Remove vinyl resist from the glass — peel carefully, starting from corners
  2. Clean the glass with isopropyl alcohol to remove any adhesive residue
  3. Evaluate the finished piece:
  4. Is the frosted area even and consistent? (Uneven = insufficient cream or poor application)
  5. Are the edges of the design sharp? (Blurry edges = cream seeped under resist)
  6. Is the unetched area completely clear? (Spots = resist had gaps)
  7. Students compare results and discuss factors that affected quality
  8. Dispose of used cream, rinse water, and applicators in the hazardous waste container
  9. Remove and dispose of gloves properly — wash hands with soap and water

Discussion Points

  • How does the etching cream frost compare visually to sandblast frosting? What is different about the texture?
  • Why is the etching time critical — what happens with too little time? Too much?
  • Why must standard nitrile gloves NOT be used for this activity?
  • What would you do if etching cream splashed on your forearm?
  • How does acid etching depth compare to rotary or sandblast engraving?

Expected Outcomes

  • Students produce a cleanly etched glass piece with sharp-edged, evenly frosted design areas
  • Students demonstrate proper chemical safety protocol throughout the activity
  • Students understand the relationship between cream application quality and etch evenness
  • Students can explain the chemical mechanism (bifluoride → HF → silica dissolution)

Assessment Rubric

Criteria Excellent (4) Proficient (3) Developing (2) Beginning (1)
Safety compliance Full PPE worn correctly throughout, proper handling and disposal Minor lapses, self-corrects immediately Needs reminders about gloves or handling Safety violations or resistant to protocols
Resist application Clean edges, no seepage, design sharp and well-positioned Mostly sharp edges, minor seepage in 1-2 spots Noticeable seepage or poorly adhered resist Resist failed, design unclear
Etch quality Even, consistent frosting across all exposed areas Mostly even, minor variations Noticeably uneven frosting Patchy or incomplete etch
Cleanup and disposal All materials properly disposed, workspace clean, hands washed Minor items missed, corrects when noted Incomplete cleanup Materials left out or improperly disposed

Safety Considerations

  • Chemical-resistant gloves (neoprene or butyl rubber) are MANDATORY — NOT nitrile, NOT latex
  • Safety glasses or splash goggles are MANDATORY throughout cream handling
  • Calcium gluconate gel must be immediately accessible — check before starting
  • If cream contacts skin: rinse with water for 5 minutes, apply calcium gluconate, notify instructor
  • If cream contacts eyes: flush with water for 15 minutes at eyewash station, seek medical attention immediately
  • Work in ventilated area — etching cream releases mild fumes
  • Do not eat, drink, or touch face while working with etching cream
  • Dispose of all etching materials (used cream, rinse water, applicators, gloves) in hazardous waste container
  • Wash hands thoroughly with soap and water after removing gloves
  • Do not mix etching cream with other chemicals
  • Students with known fluoride sensitivity or skin conditions should consult instructor before participation

Last Updated: 2026-03-19