Below are some information about glass stem and Iron wire glass:
Because glass stem for oversized Edison light bulbs is fragile, and easy to break during transportation, so some companies replace the glass stem by a iron wire or other material, iron wire is the most used for replacing glass tube stem of oversized Edison light bulbs. Iron wire stem has following features:
1. Iron wire is strong enough, so no breaking or damage at all, with this iron stem oversized Edison light bulbs is much safe for transporting.
2. Iron wire stem is cheaper than glass tube stem, because iron wire is cheaper and easy to make. That is why oversized Edison light bulbs with iron stem usually has a lower price.
3. Iron wire is with dark grey color or metal color, not transparent, so we can clearly see the iron stem inside the oversized Edison light bulbs, which is not good looking. Glass tube stem is same glass as the glass bulb, transparent, looks much more beautiful than iron wire stem.
4. Iron wire stem is elastic, but not same elastic as steel wire, iron wire is easy to change the shape, for example, stem is usually straight, but iron stem is easy to be angled during transportation, because all the filament led is fitted on the iron wire stem, it is much heavy loaded. But why we can not use hard elastic steel wire? Because steel wire is not easy to handle during production, it is too hard and strong, so we can only use iron wire for oversized Edison light bulbs.
5. Iron wire will change to black color after some time using, because of oxidation.
From above analyzing, though glass stem is easy to break, but it is much more beautiful! We can solve the breaking problem. Iron wire stem is safe enough, but it is not good looking. As a kind of decorative vintage Edison Led light bulb, beautiful looking is very important to oversized Edison light bulbs.