One of the most difficult surfaces to glue a material to is glass. Glass is extremely smooth and not as porous as other materials such as plastic or wood. Standard household glues require a rough surface to bond to which is why they don't work well on glass. Aluminium can be difficult to glue for similar reasons. Use a few simple techniques and specialised glues to adhere glass to aluminium.
Prepare the aluminium. Aluminium naturally oxidises when exposed to air. Therefore, you must remove any oxidation from the area being glued. Paint and other finishes also create a barrier that will inhibit bonding. Use a metal putty knife to scrape off any paint or finish from the aluminum's bonding surface. After scraping the majority of the finish off, continue by sanding the surface being bonded with 600-grit sandpaper until the raw aluminium is exposed. If the aluminium is unfinished, lightly sand the bonding surface with 600-grit sandpaper to remove any oxidation.
Clean the aluminium. Mix 4 tsp of dish washing soap with 946ml. of hot water. Dip a clean cotton rag into the solution. Wring the rag out. Wipe down the sanded aluminium surface to remove any sanding debris. Dry the surface with a clean cotton rag.
Wash the glass. Scrape off any debris from the glass, such as paint, with a metal putty knife. Using the same soapy water solution, wash off the area being bonded. Dry the glass off with a clean cotton rag.
Mix the epoxy. Epoxies are a two-part glue. Mix equal parts of epoxy and hardener into a small plastic container. Use a tongue depressor to mix the epoxy thoroughly. Some epoxies require a specific mixing ratio of epoxy to hardener. Follow the manufacturer's instructions if the mixing ratio is not in equal increments.
Apply the glue. Using a tongue depressor, apply epoxy to one of the surfaces being bonded. Cover the entire surface being glued to ensure a complete bond. Spread the epoxy out into a thin layer using the metal putty knife.
Join the aluminium and the glass. If bonding on a vertical surface, use either painter's masking tape or spring clamps to hold the object in place. If gluing aluminium to glass, position the aluminium object in the correct spot and apply a small amount of pressure to further spread the epoxy. Apply either painter's masking tape or spring clamps to the aluminium to hold it in place. Allow a full 24 hours drying time.
Only use epoxy formulated for glass and metal. The chemical composition of this type of epoxy is designed for adhering non-porous materials.