Therefore the question arises, what is the purpose of heat and do you need a specific conditioner? Over to the Panel
Ktani: Heat is helpful
Heat (even body heat) lifts the hair cuticle somewhat. I definitely thinks that helps products penetrate better than they would otherwise. What makes a conventional product a "deep conditioner" is more emollients, oils, and richer ingredients on average but most conditioners left on longer can saturate the hair better and be as effective used the same way, depending on the formulation.
I do not think it is a question of just oil or water that we want to penetrate hair. For plants there are a number of constituents that all play a part that can help condition hair. For conventional products the key is in the formulation. Conventional products can contain proteins that are able penetrate hair more deeply today than previoulsly and that can help strengthen it but a balance is needed between the strength and moisturization of hair to keep it supple. Oils can play a part in helping to prevent moisture loss, protein loss and lubricate hair
Laquita: No specific conditioner for deep conditioning but yes to oils and water
Now since I use all types of conditioners - I don't feel that a specific type of conditioner is more effective than another. I have experienced using some conditioners with more added oils than others and those with less oils (I have since started adding a little extra to these) like the less expensive Suave or Herbal Essence - don't leave my hair as moisturized and soft after air drying. All in all, I would say I would like both oil and water to be penetrated into my hair - the water to keep it moisturized and the oil to seal in the moisture.
Monique: Heat helps some deep conditioners
The conditioner that I use (Aubrey Organics HSR) can be used as a regular conditioner or a deep conditioner, depending on the application. Thus, I don't believe you need a specific type of conditioner. I think that heat does help make some deep conditioners more effective, I agree with Ktani about heat lifting the hair cuticle. I found a patent regarding Silicone-Conditioners and heat application, it states that the heat is one of the reasons why the conditioner is effective. The patent states that the "Silicone agents are responsible for a heat-induced reduction in bending modulus or softening of the hair." The product I use does not contain any silicones, heat may/may not help.
Noire: Mild heat may be helpful and some oils and water are definitely a good combination
Everyone's hot and cold is different. Relatively speaking, I would say mild heat would be enough help to penetrate into hair. I would agree with Ktani about the constituents play a part, and not all oils are good for for deep conditioning. I think however that "oil and water do mix" when it comes to conditioning hair, they are the most excellent combination.
Jc: Protein conditioners may be more effective with heat otherwise heat is just a placebo
Interesting points you raise Ktani specifically about proteins. From the work I have seen, proteins adsorb (yes with a D meaning stick to) super quickly onto the surface (under a second). However they are generally too large to be useful for hair and this is why they are hydrolyzed so they can fill out gaps in the hair. Small hydrolyzed protein can certainly penetrate hair and perhaps in this case heat and time would be useful I think for most commercial conditioners, heat may just be a prophylactic effect creating a feeling of softness.
I do think that penetration into hair is limited. Hair is designed to be a small fortress and resist infiltration. Very few, very small particles like some oils and water can get through. However conditioners are generally designed to work on the outside of hair and the surfactants and emollients in them simply stay outside.
1. Monique provided - Patent reference number: 5968286; Filing date: Oct 3, 1997; Issue date: Oct 19, 1999 .
2. Ktani provided - http://www.pharmpress.com/shop/samples/Eval_Herb_Med_Prod_sample.pdf, http://journal.scconline.org/pdf/cc2003/cc054n02/p00175-p00192.pdf, http://www.ncbi.nlm.nih.gov/pubmed/17520153
3. Extra reading on protein conditioners - (Go on use the search button :))