

Got a light bulb question; picture is for reference
Hey friends! I know some of yall have seen my posts as of late with my lava lamp thrifting finds. I got a question.
My middle lava lamp is a 1974 century.
The my century to the right is a screw cap and I can’t find the date.
And the aristocrat to the left of my old century is from the 90s. It’s my understanding that all of these lamps require a 40 W a15 appliance bulb. However, the aristocrat and the 90s century are really overheating. And making the wax extremely bubbly.
My question is: Do I have to use a 40W a15 bulb, or can I just use a 40W bulb? The 1974 century I recently thrifted came with a small 40W bulb and it seemed to be working fine with a normal lava flow and hasn’t been overheating. Im sort of leaning on just buying more of these 40W bulbs, but I don’t want to risk ruining the lamps or worse, causing them to explode. Alternatively, I take it I probably need to buy dimmers for the aristocrat and 1990s century? Thanks.