Hot answers tagged glue
Have you considered screwing your decorations to the metal stand, using Technic brick holes to pass the screws? If done properly no harm is done to the bricks, and you will not fear a bad glue joint!
I'm always hesitant to recommend gluing LEGO as it is so much against the spirit of LEGO. Have you considered using the magnet bricks? They come in several regular LEGO brick sizes, and they stick to metal surfaces just fine. If you must use glue, most glues will readily stick to the plastic, so that is no problem. What you need to check is what glues work ...
There are three factors you have to consider here: the possible chocking hazard for your child, the possible toxicity of the glue to your child, and the degree of removability of the glue. I don't think there exist a glue that is (1) completely secure (i.e. won't allow small parts to become chocking hazards), (2) safe to be handled and possibly ingested, ...
Your question doesn't explain why you want to glue the models for a 4 year old, so I'm going to go ahead and advocate that you don't glue and instead let your 4 year old build. 4 years old is a great time to be learning the fine motor skills, geometry, physics, colour and esthetics, not to mention creativity and storytelling. Gluing the models takes away ...
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