Solid products have moved from the hardcore backpacker/environmentalist niche to being the new hot thing, so I wanted to write a little about my experience with them.
The big plus point for solid bar products is their lower environmental impact-- low to no packaging, instead of a big plastic bottle, half of which is water that is transported halfway around the globe, you get a little bar in a cardboard box. Solid beauty products are dry and concentrated, this imo justifies the often slightly higher cost-- they usually last longer, volume-wise.
But lets talk about ingredients. Solid products usually don't need preservatives, because they are dry. Other than that, the formulations are often very different than those of conventional products. It's also important to note that a solid product is not automatically natural -- seem of them contain ingredients like SLS so make sure you check the ingredient list or look for products organic certificates.
Solid shower gel
I love these so much. While regular soaps are formulated to get heavier dirt off your hands (from cooking, cleaning, etc), solid bath gels are much gentler and usually have a neutral pH level. Unlike soap, they don't dry your skin and feel pretty much like regular shower gel when you wet them. They feel luxurious and creamy, just like shower gels. I love them so much that I don't think I'll be switching back to regular soap for my body again.
Solid body moisturisers aka lotion bars:
Lotion bars are very moisturising and you should absolutely try them if your skin is dry. They are best used after showering or while actually in the shower. Combined with heat and water they go on easily and seal in the moisture. I like to rub the block in my hands as if I were lathering soap, this makes the bar melt. Then I apply as usual. I feel like the lotion bars seal in the moisture very effectively, and in the winter I feel like they keep me warmer. This might sound weird but someone pointed out that when your lips are cold and you apply balm, they stop feeling cold. So it's kind of like that. The downside is that the application does take a couple of extra minutes, and is not so nice if your skin isn't wet. Anyway, I don't think my skin has ever been so moisturized as it has been this winter.
Solid hair soaps and shampoos
These are actually two very different products. Hair soap is soap, it has a basic pH level and honestly I haven't met any hair-care addict who was happy with it. As it raises the pH level of the hair, you need to rinse your hair with vinegar to neutralise the pH level. This shifting pf pH levels isn't kind to the hair long-term. Hair soap also performs really badly with hard water.
Solid shampoo is formulated much closer to shampoo. There are a lot of very different formulations out there, so it might take some testing to find one your hair likes. Most of them give the hair more texture than slip, and can leave the hair a bit matte and cause build-up over time. However there are plenty of people who swear by shampoo bars, so if you feel like giving them a try, do! Pick ones without sulfates or sodium bicarbonate. Other ingredients to look out for is protein -- some hair types love it some hat it, I wrote more about that here. In the German-speaking market the
Solid hair conditioners
These are formulated with solid ingredients such as coconut oil, shea butter or stearyl alcohol, which makes them heavy. To solve this, some manufacturers add ingredients such as sulfates to make the bar lather, which is not very kind to the hair. I feel that if your hair is very dry, you can try out hair conditioners in a bar. If your hair is easily weighed down, skip this category.
Solid Deodorant
This is a very individual product -- I find that natural deodorants are so personal, what one person swears by may not work for another person at all. Personally I have had a lot of success with the solid deodorants from Lush.
Solid toothpaste
Fun! There are a couple of kinds out there -- while for travelers the little tablets are the most practical, I personally like powders a lot. There is also tooth soap, and while it tastes disgusting it has helped me with some gum issues. I don't really want to give out much advice here as this is more of a medical product than a beauty product, but I really encourage you to explore low-waste tooth care.