Focus, Jill, focus! Yes, the main point of this blog post is about hot irons (this also applies to curling irons) and whether they will damage your grey. The fact of the matter is that you need to rethink your approach to styling tools and products. You rethought product to protect your dyed hair and now you have natural, uncoated hair with little to no melanin. This needs to be considered. See? Even Tony is adjusting the temperature settings on his flat iron.
The first thing I would like to point out is stop listening to people tell you you have to stop blow drying your hair, or that you have to accept the curls that drove you to the flat iron in the first place. You have options and choose whatever option works for you. I hate being told that I should embrace my curls. Don't wanna. Ain't gonna. I have control over very little in my life and so I take out these control issues on my hair.
Point number two is that you're not going to necessarily burn or yellow your hair just because you use a styling tool. I'm going to lay out my much researched information to dissuade this from happening. When I first heard this discussed on Cafe Gray I knew it not to be true. After all, my mom had gray hair for 30 years, blew it dry every other day, and curled it EVERY SINGLE day. Never once was it anything less than brilliant silver and white.
Mom didn't buy high-end styling tools but I recommend that you get a good styling tool with a heat setting dial. I also recommend that you get a blow dryer with a cool or cold setting. Now a disclaimer is that I am not a hair stylist so this is just my research, what I've learned calling and talking to various stylists, and my own personal experience. So I recommend you take this to your stylist and get his/her opinion as well.
One should never go over 300 degrees F. You might have wiry forest children sticking up but they will soon calm down. Normally they stick up because they are new growth, short, and have no tribe. So they need to be coaxed into a tribe and then they will soon be well-behaved gray hairs. Hair starts to literally melt at any temperature above 420 degrees so you can see what 120 degrees difference makes. Why not over 300? You have very little melanin in your hair now and the high heat can burn it easier. I personally never go over 265-285 and I had coarse, curly hair. Now it's medium textured and curly.
Try to buy styling products specifically for grey or platinum hair. A lot of products can create a build-up or even tint your hair and the combination with heat will just seal them in. That is why I NEVER put on any styling product right before I style my hair. I typically put on a serum after washing my hair, sleep and let it air dry, then iron in the morning. I too need to reevaluate my styling products and trash a great majority of them. If you're going to blow dry then put on your styling product and let it air dry for at least 15 minutes before you use the dryer.
This will probably get me hate mail but here goes. I think your keratin and Brazilian blow out days are over. Remember what I said about hair melting at 420 degrees? Well Keratin and Brazilian blow outs use irons at 450 degrees or higher. It fuses the formaldehyde or aldehyde to your hair and can easily cause permanent damage whether you have colored hair or grey.
Clean Your Iron
Every week, clean your iron. I use mine twice a week, and I might use it 1-2 times more on the nape of my neck on those mornings where I must have had really rockin' dreams. Take a cotton ball with rubbing alcohol and clean any build up from product. The cleanliness of your styling tool will ensure that it won't be sealing any product on your hair and thus damaging it.
This is the most important tip: do a heat test before you use your flat iron. Take a piece of tissue paper and get it damp. Hold it in your iron for 10-20 seconds. If it sizzles and yellows the paper, it can do that to your hair. If the paper comes out white, it won't discolor your hair.
You can't always reverse damage. Sometimes if it's a matter of sealing product buildup on your hair, you can put baking soda and purple shampoo on your hair for 15-30 minutes and it will brighten again. You can substitute baking soda for a vitamin C packet like Emergen-C as well. It might take a few times but always worth a shot.
This is the anal retentive guide to using styling tools on your silver. Remember, my mom used them every day of her life, and she bought her utensils at drug stores. They weren't costly, they weren't the highest setting, but in her 30 years I never remember her once damaging her hair to the point of being yellowed. But if you're paranoid like me, clean your styling tool and do the damp toilet paper test. And then you have more options if you want a sleek, straight look.